1. II – UNIT Procedure Oriented Programming
Object Oriented Programming Paradigm
Basic Concepts of OOPS
Benefits of OOPS
Class fundamentals
Declaring Objects
7.Assigning Object References
8. Introducing Methods
9. Constructors
10. this keyword
11. Garbage Collection
12. finalize ( ) Method
13. Overloading Methods
14. Object as parameters
15. Returning Objects
16. Access Control
17. static and final keyword
18. Nested classes and Inner Class
19. Classes with Command Line
arguments
20.Packages
21.Enums in Java

2. PROCEDURE ORIENTED PROGRAMMING
1. In Procedural programming, Programmer combines related sequences of statements into one single place, called procedure.
2. A procedure call is used to invoke the procedure.
3. After the sequence is processed, flow of control proceeds right after the position where the call was made.
4. But the approach in oops is that classes and objects are used to model real world entity taking help of methods which performs the functions.
5. This technique is also known as Top – down programming
OBJECT ORIENTED PROGRAMMING PARADIGM
1. The major objective of object oriented approach is to eliminate some of the flaws encountered in the procedural approach.
2. OOP treats data as a critical element to the program development and does not allow it to flow freely around the system.
3. It ties data more closely to the function that operate on it an protects it from unintentional modification by other functions.

3. 4. OOP allows us to decompose a problem into a number of entities called Objects and then build data and functions (known as methods in Java) around these entities.
5. The combination of data and methods make up an object
Methods
Data
Object = Data + Methods
6. The data of an object can be accessed only by the methods associated with that object.
7. However, methods of one object can access the methods of other object.

4. Procedural vs. Object-Oriented
Withdraw, deposit, transfer
Customer, money, account

5. Procedural vs. Object-Oriented – Contd.,
Real world Objects are mapped to software in OOPs
Objects in the problem domain are mapped to objects in software
011101
10011
11101
11010
010101
10101

6. Questions
What are Objects?
What are Classes?
What are Messages?

7. Answers Objects reflect instances that embody those concepts.
Classes reflect concepts.
Messages are communication between objects.
object
class
Mita
Gita
Rita
Sita

8. What are Objects?
“An object is a software bundle of variables and related methods”
Software objects are model real-world objects or abstract concepts
Real-world objects have states and behaviors
Dogs' states: name, color, breed, hungry
Dogs' behaviors: barking fetching
Software objects implement real-world objects by:
Using variables to implement states
Using methods to implement behaviors

9. Visual Representation of a Software Object

10. 8. Some of the features of object oriented paradigm are:
Emphasis is on data rather than procedure.
Programs are divided into what are known as Objects.
Data Structures are designed such that they characterize the objects.
Methods that operate on the data of an object are tied together in the data structure.
Data is hidden and cannot be accessed by external functions.
Objects may communicate with each other through methods.
New data and methods can be easily added whenever necessary.
Follows bottom – up approach in program design.
9. Our definition of object oriented programming is: Object oriented programming is an approach that provides a way of modularizing programs by creating partitioned memory area for both data and function that can be used as templates for creating copies of such modules on demand.

11. BASIC CONCEPTS OF OBJECT ORIENTED PROGRAMMING
Class Objects 3. Data Abstraction
4. Data Encapsulation 5. Data Hiding 6. Inheritance
7. Polymorphism 8. Dynamic Binding
9. Message Communication
Class
The entire set of data and code of an object can be made a user – defined data type using the concept of a class. A class may be thought of as a ‘data type’ and an object as a ‘variable’ of that data type. Once a class has been defined, we can create any number of objects belonging to that class. Each object is associated with the data of type class with which they are created. A class is thus a collection of objects of similar type.
2. Objects
Objects are the basic runtime entities in an object – oriented system. They may represent a person, a place, a bank account, a table of data or any item that the program may handle. They may also represent user – defined data types such as vectors and lists. Any programming problem is analyzed in terms of objects and the nature of communication between them.

12. What are Classes?
A class is a blueprint or prototype defining the variables and methods common to all objects of a certain kind.
An object is an instance of a certain class.
After you have created a class, you must create an instance of it before you can use.
The benefit of Classes: Reusability
A class captures the common properties of the objects instantiated from it
A class characterizes the common behavior of all the objects that are its instances

13. Representation of an object
Person
Name
BasicPay
Salary()
Tax()
Object
Data
Methods
Representation of an object
3. Data Abstraction, 4. Data Encapsulation and 5. Data Hiding
The wrapping up of data and methods into a single unit is known as encapsulation. Data encapsulation is the most striking feature of a class. The data is not accessible to the outside world and only those methods, which are wrapped in the class, can access it, these methods provide the interface between the object’s data and the program,

14. This insulation of the data from direct access by the program is called data hiding. Encapsulation makes it possible for objects to be treated like ‘black boxes’, each performing a specific task without any concern for internal implementation.
Data
And
Method
Information “in”
Information “out”
Abstraction refers to the act of representing essential features without including the background details or explanations. Classes use the concept of abstraction and are defined as a list of abstract attributes such as size, weight and cost, and methods that operator on these attributes, They encapsulate all the essential properties of the objects that are to be created.
6. Inheritance
Inheritance is the process by which objects of one class acquire the properties of objects of another class. Inheritance supports the concept of hierarchical classification. In OOP, the concept of inheritance provides the idea of reusability. This means that we can add additional features to an existing one. The new class will have the combined features of both the classes.

15. Thus the real appeal and power of the inheritance mechanism is that it allows the programmer to reuse a class that is almost, but not exactly, what he wants, and to tailor the class in such a way that it does not introduce any undesirable side effects into the rest of the classes. In java, the derived class is known as ‘subclass’
Bird
Attributes:
Feathers
Lay eggs
Flying Bird
Non FlyingBird

16. 7. Polymorphism
Polymorphism is another important OOP concept. Polymorphism means the ability to take more than one form. For example, an operation may exhibit different behaviour in different instances. The behaviour depends upon the types of data used in the operation. For example consider the operation of addition. For two number, the operation will generate a sum. If the operands are strings, then the operation would produce a third string by concatenation. Consider the following example:
Shape
Draw()
Circle Object
Draw(circle)
Box Object
Draw(box)
Triangle Object
Draw(triangle)
Polymorphism plays an important role in allowing objects having different interval structures to share the same external interface. This means that a general class of operations may be accessed in the same manner even though specific actions associated with each operation may differ. Polymorphism is extensively used in implementing inheritance.

17. Dynamic Binding
Binding refers to the linking of a procedure call to the code to be executed in response to the call. Dynamic binding means that the code associated with a given procedure call is not known until the time of the call at runtime. It is associated with polymorphism and inheritance. A procedure call associated with a polymorphic reference depends on the dynamic type of that reference.
Message Communication
An object – oriented program consists of a set of objects that communicate with each other. The process of programming in an object – oriented language, therefore, involves the following basic steps:
1. Creating classes that define objects and their behaviour
2. Creating objects from class definitions.
3. Establishing communication among objects.
Objects communicate with one another by sending and receiving information much the same way as people pass messages to one another. The concept of message passing makes it easier to talk about building systems that directly model or simulate their real world counterparts.

18. Network of objects communicating between them

19. Benefits of OOPS
1. Through inheritance, we can eliminate redundant code and extend the use of existing classes.
2. We can build programs from the standard working modules that communicate with one another, rather than having to start writing the code from scratch. This leads to saving of development time and higher productivity.
3. The principle of data binding helps the programmer to build secure programs that cannot be invaded by code in other parts of the program.
4. It is possible to map objects in the problem domain to those objects in the program.
5. It is possible to have multiple objects to coexist without any interference.
6. It is easy to partition the work in a project based on objects.
7. The data – centered design approach enables us to capture more details of a model in an implementable form.
8. Object – Oriented systems can be easily upgraded from small to large systems.
9. Message passing techniques for communication between objects make the interface descriptions with external systems much simpler.
10. Software complexity can be easily managed.

20. Application of OOPS 1. Real – time systems.
2. Simulation and modelling.
3. Object – oriented databases.
4. Hypertext, hypermedia and expertext.
5. AI and expert systems.
6. Neural networks and parallel programming.
7. Decision support.
8. Office automation systems.
9. CIM / CAD / CAM system.

21. The Java Buzzwords or Java Features or Java Characteristics
■ Simple
■ Secure
■ Portable
■ Object-oriented
■ Robust
■ Multithreaded
■ Architecture-neutral
■ Interpreted
■ High performance
■ Distributed
■ Dynamic 21

22. Methods Introductions

23. Introduction Methods are nothing but function.
It is a set of statements which can be included in java class.
It can be called at any point in java class by simply calling method name.
Methods have so much of power and flexibility.
Methods should be declared in the class.
It can be public, private, and protected.
Methods are of two types, one is with argument and another is without argument.

24. Types of Methods
Methods are used to access the data fields in a class
These methods are linked with the objects
Class creates an object using new keyword, and this object can be used for calling the methods.
An instance method is called by prefixing it with an object

25. Methods can be declared using various types such as
1. Return type method -returns value or does not return any values (void).
2. Modifiers – it is public private, and protected
3. Parameter – it should be listed in parentheses,().
4. Method body – declare between braces
Method declaration
static - class method, no need to create class reference
final - method cannot be overridden
abstract - method is not implemented in another cl
ass/method

26. Empty Method Output : Result K is 100
class emptymethod { int i,j,k; void method1() { i=10; j=10; k=i*j; System.out.println(" Result k is:"+k);} public static void main(String args[]) { emptymethod e=new emptymethod(); e.method1(); }}
Output :
Result K is 100

27. Method using argument
class argument { int i; String st; void meth(int a, String s) { int i=a; String st=s; System.out.println("Employee Id:"+i); System.out.println("Employee Id:"+st); } public static void main(String args[]) { argument obj=new argument(); obj.meth(5001,"Kumar"); }}

28. Methods using return keyword
class example { int c; int add(int a, int b) { return a+b; } int subtract(int a, int b){ return a-b;} int multiply(int a, int b){ return a*b;} int division(int a, int b) { return a/b; }}
class returnexa { public static void main(String[] args) { example obj= new example(); obj.add(10,20); System.out.println("Addition: " +obj.add(30,15)); System.out.println("Subtraction: " +obj.subtract(30,15)); System.out.println("Multiplication: " +obj.multiply(30,15)); System.out.println("Division: " + obj.division(30,15)); }}

29. CLASS FUNDAMENTALS

30. The General Form of a Class
Class contains data and the code that operates on that data.
While very simple classes may contain only code or only data, most real-world classes contain both.
A class is declared by use of the class keyword. The general form of a class definition is shown here:
class classname {
type instance-variable1;
type instance-variable2;
// ...
type instance-variableN;
type methodname1(parameter-list)
// body of method }
type methodname2(parameter-list)
type methodnameN(parameter-list)

31. // APPLICATION OF CLASSES AND OBJECTS
using System;
class Rectangle {
public int length, width;
public void GetData(int x,int y)
length = x;
width = y; }
public int RectArea ()
int area = length * width;
return (area);
class RectArea
public static void Main()
int area1,area2;
Rectangle rect1 = new Rectangle ();
Rectangle rect2 = new Rectangle ();
rect1.length = 15;
rect1.width = 10;
area1 = rect1.length * rect1.width ;
rect2.GetData (20,10);
area2 = rect2.RectArea ();
System.out.println("Area1 = " + area1);
System.out.println("Area2 = " + area2);

32. Assigning Object Reference Variables
Object reference variables act differently than you might expect when an assignment takes place. For example, what do you think the following fragment does?
Box b1 = new Box();
Box b2 = b1;
You might think that b2 is being assigned a reference to a copy of the object referred to by b1. That is, you might think that b1 and b2 refer to separate and distinct objects. However, this would be wrong. Instead, after this fragment executes, b1 and b2 will both refer to the same object. The assignment of b1 to b2 did not allocate any memory or copy any part of the original object. It simply makes b2 refer to the same object as does b1. Thus, any changes made to the object through b2 will affect the object to which b1 is referring, since they are the same object. This situation is depicted here:
Although b1 and b2 both refer to the same object, they are not linked in any other way. For example, a subsequent assignment to b1 will simply unhook b1 from the original object without affecting the object or affecting b2. For example:
Box b1 = new Box();
Box b2 = b1;
// ...
b1 = null;
Here, b1 has been set to null, but b2 still points to the original object.

33. ADDING METHODS class Box { double width; double height; double depth;
// display volume of a box
void volume()
System.out.print("Volume is ");
System.out.println(width * height * depth); }
class BoxDemo3
public static void main(String args[]
Box mybox1 = new Box();
Box mybox2 = new Box();

34. // assign values to mybox1's instance variables
mybox1.width = 10;
mybox1.height = 20;
mybox1.depth = 15;
/* assign different values to mybox2's instance variables */
mybox2.width = 3;
mybox2.height = 6;
mybox2.depth = 9;
// display volume of first box
mybox1.volume();
// display volume of second box
mybox2.volume(); }

35. Returning a Value class Box { double width; double height;
double depth;
// compute and return volume
double volume()
return width * height * depth; }
class BoxDemo4
public static void main(String args[])
Box mybox1 = new Box();
Box mybox2 = new Box();
double vol;

36. // assign values to mybox1's instance variables
mybox1.width = 10;
mybox1.height = 20;
mybox1.depth = 15;
/* assign different values to mybox2's instance variables */
mybox2.width = 3;
mybox2.height = 6;
mybox2.depth = 9;
// get volume of first box
vol = mybox1.volume();
System.out.println("Volume is " + vol);
// get volume of second box
vol = mybox2.volume(); }

37. Adding a Method That Takes Parameters
class Box {
double width;
double height;
double depth;
// compute and return volume
double volume()
return width * height * depth; }
// sets dimensions of box
void setDim(double w, double h, double d)
width = w;
height = h;
depth = d;

38. class BoxDemo5 {
public static void main(String args[]) {
Box mybox1 = new Box();
Box mybox2 = new Box();
double vol;
// initialize each box
mybox1.setDim(10, 20, 15);
mybox2.setDim(3, 6, 9);
// get volume of first box
vol = mybox1.volume();
System.out.println("Volume is " + vol);
// get volume of second box
vol = mybox2.volume(); }

39. Constructors class Box { double width; double height; double depth;
// This is the constructor for Box.
Box()
System.out.println("Constructing Box");
width = 10;
height = 10;
depth = 10; }
// compute and return volume
double volume()
return width * height * depth;

40. class BoxDemo6 {
public static void main(String args[])
// declare, allocate, and initialize Box objects
Box mybox1 = new Box();
Box mybox2 = new Box();
double vol;
// get volume of first box
vol = mybox1.volume();
System.out.println("Volume is " + vol);
// get volume of second box
vol = mybox2.volume(); }

41. Parameterized Constructors
class Box {
double width;
double height;
double depth;
// This is the constructor for Box.
Box(double w, double h, double d)
width = w;
height = h;
depth = d; }
// compute and return volume
double volume()
return width * height * depth;

42. class BoxDemo7 {
public static void main(String args[])
// declare, allocate, and initialize Box objects
Box mybox1 = new Box(10, 20, 15);
Box mybox2 = new Box(3, 6, 9);
double vol;
// get volume of first box
vol = mybox1.volume();
System.out.println("Volume is " + vol);
// get volume of second box
vol = mybox2.volume(); }

43. The this Keyword Garbage Collection
Sometimes a method will need to refer to the object that invoked it. To allow this, Java defines the this keyword. this can be used inside any method to refer to the current object. That is, this is always a reference to the object on which the method was invoked. You can use this anywhere a reference to an object of the current class’ type is permitted. To better understand what this refers to, consider the following version of Box( ):
// A redundant use of this.
Box(double w, double h, double d) {
this.width = w;
this.height = h;
this.depth = d; }
Garbage Collection
Since objects are dynamically allocated by using the new operator, you might be wondering how such objects are destroyed and their memory released for later reallocation. In some languages, such as C++, dynamically allocated objects must be manually released by use of a delete operator. Java takes a different approach; it handles deallocation for you automatically. The technique that accomplishes this is called garbage collection.

44. The finalize( ) Method
The constructor method is used to initialize an object when it is declared. This process is known as initalisation. Similarly, Java supports a concept called finalization, which is just opposite to initialization. We know that java run – time is an automatic garbage collecting system. It automatically frees up the memory resources used by the objects. But objects may hold other non – object resources such as file descriptors or window system fonts. The garbage collector cannot free these resources. In order to free resources we must use a finaliser method. This is similar to destructor in C++.
The finalize( ) method has this general form:
protected void finalize( ) {
// finalization code here }

45. Overloading Methods class OverloadDemo { void test()
System.out.println("No parameters"); }
// Overload test for one integer parameter.
void test(int a)
System.out.println("a: " + a);
// Overload test for two integer parameters.
void test(int a, int b)
System.out.println("a and b: " + a + " " + b);
// overload test for a double parameter
double test(double a)
System.out.println("double a: " + a);
return a*a;

46. class Overload {
public static void main(String args[])
OverloadDemo ob = new OverloadDemo();
double result;
// call all versions of test()
ob.test();
ob.test(10);
ob.test(10, 20);
result = ob.test(123.25);
System.out.println("Result of ob.test(123.25): " + result); }

47. Overloading Constructors
class Box {
double width;
double height;
double depth;
// constructor used when all dimensions specified
Box(double w, double h, double d)
width = w;
height = h;
depth = d; }
// constructor used when no dimensions specified
Box()
width = -1; // use -1 to indicate
height = -1; // an uninitialized
depth = -1; // box

48. // constructor used when cube is created
Box(double len) {
width = height = depth = len; }
// compute and return volume
double volume()
return width * height * depth;
class OverloadCons
public static void main(String args[])
// create boxes using the various constructors
Box mybox1 = new Box(10, 20, 15);
Box mybox2 = new Box();
Box mycube = new Box(7);
double vol;

49. // get volume of first box
vol = mybox1.volume();
System.out.println("Volume of mybox1 is " + vol);
// get volume of second box
vol = mybox2.volume();
System.out.println("Volume of mybox2 is " + vol);
// get volume of cube
vol = mycube.volume();
System.out.println("Volume of mycube is " + vol); }

50. Using Objects as Parameters
// Objects may be passed to methods.
class Test {
int a, b;
Test(int i, int j)
a = i;
b = j; }
// return true if o is equal to the invoking object
boolean equals(Test o)
if(o.a == a && o.b == b) return true;
else return false;
class PassOb
public static void main(String args[])
Test ob1 = new Test(100, 22);
Test ob2 = new Test(100, 22);
Test ob3 = new Test(-1, -1);
System.out.println("ob1 == ob2: " + ob1.equals(ob2));
System.out.println("ob1 == ob3: " + ob1.equals(ob3));

51. Returning Objects // Returning an object. class Test { int a;
Test(int i)
a = i; }
Test incrByTen()
Test temp = new Test(a+10);
return temp;
class RetOb
public static void main(String args[])
Test ob1 = new Test(2);
Test ob2;
ob2 = ob1.incrByTen();
System.out.println("ob1.a: " + ob1.a);
System.out.println("ob2.a: " + ob2.a);
ob2 = ob2.incrByTen();
System.out.println("ob2.a after second increase: “ + ob2.a);

52. Access Specifier Accessing Level
ACCESS CONTROL
Access Specifier
Accessing Level
private
Same Class in Same Package
private protected
Sub Class in Same Package
friendly (not a keyword
Non – Sub Class in Same Package
protected
Sub Class in Other Package
public
Other Class in Other Package
class Test {
int a; // default access
public int b; // public access
private int c; // private access
// methods to access c
void setc(int i) // set c's value
c = i; }
int getc() // get c's value
return c;
} }

53. class AccessTest {
public static void main(String args[])
Test ob = new Test();
// These are OK, a and b may be accessed directly
ob.a = 10;
ob.b = 20;
// This is not OK and will cause an error
// ob.c = 100; // Error!
// You must access c through its methods
ob.setc(100); // OK
System.out.println("a, b, and c: " + ob.a + " " + ob.b + " " + ob.getc()); }

54. Understanding static
There will be times when you will want to define a class member that will be used independently of any object of that class. Normally a class member must be accessed only in conjunction with an object of its class. However, it is possible to create a member that can be used by itself, without reference to a specific instance. To create such a member, precede its declaration with the keyword static. When a member is declared static, it can be accessed before any objects of its class are created, and without reference to any object. You can declare both methods and variables to be static. The most common example of a static member is main( ). main( ) is declared as static because it must be called before any objects exist. Instance variables declared as static are, essentially, global variables. When objects of its class are declared, no copy of a static variable is made. Instead, all instances of the class share the same static variable.
Methods declared as static have several restrictions:
■ They can only call other static methods.
■ They must only access static data.
■ They cannot refer to this or super in any way.

55. class UseStatic {
static int a = 3;
static int b;
static void meth(int x)
System.out.println("x = " + x);
System.out.println("a = " + a);
System.out.println("b = " + b); }
static
System.out.println("Static block initialized.");
b = a * 4;
public static void main(String args[ ])
meth(42);

56. Static methods
These methods are not linked with instance variables of any object of the class.
Objects are defined in the static method.
A static method is called by prefixing it with a class name.
No need to create class object to call the static method because when the method are declared as static the interpreter first calls only the static method.

57. Example
class staticexample { static int x,y,z; static void meth() { x=400; y=200; z=x/y; System.out.println(" The z value is:"+ z); } public static void main(String args[]){ meth();}}

58. Static method with the arguments
class static1 { static int i,j; static String st; static void staticmeth(int a, String s, int b) { int i=a; String st=s; int j=b; System.out.println("Roll Number:"+" "+i); System.out.println("Student Name:"+" "+st); System.out.println("Age:"+" "+j); } public static void main(String args[]) { staticmeth(5001,"Kumar",25); }}

59. Class Examples
class method1 { String name, address; int age,SNO; void meth(int a, int b){ age=a; SNO=b; System.out.println ("Student Serial NO:"+SNO+" "+"Student AGE:"+age); } void meth1(String x, String y) { name=x; address=y; System.out.println("Student Name:"+name+" "+"Student Address:"+address);}}

60. Class Examples
class mainmeth{ public static void main(String st[]){ method1 obj1=new method1(); //Object/class reference created using new keyword method1 obj2=new method1(); obj1.meth(25,41); // calling method using object name obj2.meth1("Sundar","Chennai"); }}

61. Scope of Methods The scope defines whether it is needed or not.
Scope are called modifiers, and it is of four types.
Scopes are defines as per class’s scope
Scopes and types
1. Public - it can be accessed anywhere in the java program.
Eg:
public void method() {
//Body of method }

62. Scopes and types
2. Private - it can be derived only by the main class. Eg: private void method() { //Body of method } 3. Protected - it can be accessed only within the package, class and sub class protected void method()

63. Syntax Creating a string: String stringname=new String();
Creating string with characters
String stringname=newString(initialvalue);
Eg: char a[]={‘R’,’A’,’J’,’U’};
String s1=new String(a);
Creating a string with another string
String stringname= new String(stringobject);
Eg: String s={“Raju”};

64. Syntax Creating a string using substring
String stringname=new String(String,startindex,number);
Eg: char a[]={‘j’,’a’,’v’,’a’}
String s1=new string(a,4,4)
Creating a string with array of ASCII arguments
String stringname =new String(bytearray);
Eg: byte C[]={ 74,65,86,65}

65. Important methods in string class
i) int length() ii) String tolowerCase() iii) String toupperCase() iv) String trim() v) String concat(string1) vi) String replace(char c1,char c2) vii) Boolean equals(string 1) viii) Char charAt(int n) ix) int compare To (string1) x) String substring (int n) xi) String substring(int n,int m) xii) int indexOf(char chr)

66. Examples
public class StringDemo { public static void main(String args[]) { String s1="java"; String s2=s1.toUpperCase(); String s3=s1.toLowerCase(); String s4=s1.concat("red"); String s5=s1.trim(); String s6=s1.replace('b','f'); char c=s1.charAt(3); System.out.println("Original String :"+s1); System.out.println("Uppercase string :"+s2); System.out.println("Lowercase string :"+s3); System.out.println("concatenate String :"+s4); System.out.println("trimming String :"+s5); System.out.println("replaced string :"+s6); System.out.println("Character at position3 :"+c); } }

67. Assignment
1. Write a program to calculate the length of a string. 2. Write a program to compare two character arrays. 3. Write a program to sort an array? 4. Write a program to find the average of n numbers 5. Write a program to multiply two matrices.

68. Nested and Inner Classes
It is possible to define a class within another class; such classes are known as nested classes. The scope of a nested class is bounded by the scope of its enclosing class. Thus, if class B is defined within class A, then B is known to A, but not outside of A. A nested class has access to the members, including private members, of the class in which it is nested. However, the enclosing class does not have access to the members of the nested class.
There are two types of nested classes: static and non-static. A static nested class is one which has the static modifier applied. Because it is static, it must access the members of its enclosing class through an object. That is, it cannot refer to members of its enclosing class directly. Because of this restriction, static nested classes are seldom used.
The most important type of nested class is the inner class. An inner class is a non-static nested class. It has access to all of the variables and methods of its outer class and may refer to them directly in the same way that other non-static members of the outer class do. Thus, an inner class is fully within the scope of its enclosing class.

69. // Demonstrate an inner class.
class Outer {
int outer_x = 100;
void test()
Inner inner = new Inner();
inner.display(); }
// this is an inner class
class Inner
void display()
System.out.println("display: outer_x = " + outer_x);
class InnerClassDemo
public static void main(String args[])
Outer outer = new Outer();
outer.test();
} }

70. Using Command-Line Arguments
Sometimes you will want to pass information into a program when you run it. This is accomplished by passing command-line arguments to main( ). A command-line argument is the information that directly follows the program’s name on the command line when it is executed. To access the command-line arguments inside a Java program is quite easy—they are stored as strings in the String array passed to main( ). For example, the following program displays all of the command-line arguments that it is called with:
// Display all command-line arguments.
class CommandLine {
public static void main(String args[])
for(int i=0; i<args.length; i++)
System.out.println("args[" + i + "]: " + args[i]); }
Try executing this program, as shown here:
java CommandLine this is a test
When you do, you will see the following output:
args[0]: this args[1]: is args[2]: a args[3]: test
args[4]: 100 args[5]: -1

71. II – UNIT Inheritance Inheritance with Super Keyword
Inheritance with Method Overriding
Inheritance with Abstract Class
Inheritance with Final Keyword
Interfaces
Packages
String Functions
StringBuffer Functions

72. INHERITANCE

73. INHERITANCE A B What is Inheritance?
Inheritance is the mechanism which allows a class B to inherit properties/characteristics-
attributes and methods of a class A. We say “B inherits from A". A
Super Class or Base Class or Parent Class B
Sub Class or Derived Class or Child Class
What are the Advantages of Inheritance
1. Reusability of the code.
2. To Increase the reliability of the code.
3. To add some enhancements to the base class.

74. Inheritance achieved in two different forms
1. Classical form of Inheritance
2. Containment form of Inheritance
Classical form of Inheritance
We can now create objects of classes A and B independently.
Example:
A a; //a is object of A
B b; //b is object of B A
Super Class or Base Class or Parent Class B
Sub Class or Derived Class or Child Class

75. In Such cases, we say that the object b is a type of a
In Such cases, we say that the object b is a type of a. Such relationship between a and b is referred to as ‘is – a’ relationship
Example
1. Dog is – a type of animal
2. Manager is – a type of employee
3. Ford is – a type of car
Animal
Horse
Dog
Lion

76. Containment Inheritance
We can also define another form of inheritance relationship known as containership between class A and B.
Example:
class A { }
class B
A a; // a is contained in b
B b;

77. In such cases, we say that the object a is contained in the object b
In such cases, we say that the object a is contained in the object b. This relationship between a and b is referred to as ‘has – a’ relationship. The outer class B which contains the inner class A is termed the ‘parent’ class and the contained class A is termed a ‘child’ class.
Example:
1. car has – a radio.
2. House has – a store room.
3. City has – a road.
Car object
Radio object

78. 1. Single Inheritance (Only one Super Class and One Only Sub Class)
Types of Inheritance
1. Single Inheritance (Only one Super Class and One Only Sub Class)
2. Multilevel Inheritance (Derived from a Derived Class)
3. Hierarchical Inheritance (One Super Class, Many Subclasses)
1. Single Inheritance (Only one Super Class and Only one Sub Class) A B

79. 2. Multilevel Inheritance (Derived from a Derived Class)B C
4. Hierarchical Inheritance (One Super class, Many Subclasses) A B C D

80. Single Inheritance (Only one Super Class and One Only Sub Class)
class Room {
protected int length, breadth;
Room()
length = 10; breadth = 20; }
void Room_Area()
System.out.println("The Area of the Room is:" + (length * breadth));
class HallRoom extends Room
int height;
HallRoom()
length = 10;
breadth = 20;
height = 30;
void HallRoom_Volume()
System.out.println("The Valoume of the HallRoom is:" + (length * breadth * height));

81. class MainRoom {
public static void main(String [] args)
HallRoom hr = new HallRoom();
hr.Room_Area();
hr.HallRoom_Volume(); }

82. Multilevel Inheritance (Derived from a Derived Class)
class Room {
protected int length, breadth;
Room()
length = 10;
breadth = 20; }
void Room_Area()
System.out.println("The Area of the Room is:" + (length * breadth));
class HallRoom extends Room
int height;
HallRoom()
length = 10; breadth = 20; height = 30;
void HallRoom_Volume()
System.out.println("The Volume of the HallRoom is:" + (length * breadth * height));

83. class BedRoom extends HallRoom{
int height_1;
BedRoom()
length = 10; breadth = 20; height = 30;
height_1 = 40; }
void BedRoom_Volume1()
System.out.println("The Volume of the the BedRoom is:" + (length * breadth * height * height_1));
class MainRoom
public static void main(String [] args)
BedRoom br = new BedRoom();
br.Room_Area();
br.HallRoom_Volume();
br.BedRoom_Volume1();

84. Hierarchical Inheritance (One Super Class, Many Subclasses)
class Room {
protected int length, breadth, height;
Room()
length = 10;
breadth = 20;
height = 30; }
class HallRoom extends Room
void HallRoom_Area()
System.out.println("The Area of the HallRoom is:" + (length * breadth));

85. class BedRoom extends Room{
void BedRoom_Volume()
System.out.println("The Volume of the BedRoom is:" + (length *
breadth * height)); }
class MainRoom
public static void main(String [] args)
HallRoom hr =new HallRoom();
BedRoom br = new BedRoom();
hr.HallRoom_Area();
br.BedRoom_Volume();

86. INHERITANCE WITH super KEYWORD

87. The purpose of the ‘super’ keyword:
1. Using super to call Superclass Constructors
2. Using super to call Superclass Methods
Using super to Call Superclass Constructor
A Subclass can call a constructor method defined by its superclass by use of the following form of super:
super (parameter – list)
Here, parameter – list specifies any parameter needed by the constructor in the superclass, super() must always be the first statement executed inside a subclass constructor.
Restriction of the Subclass constructor
1. super may only be used within a subclass constructor method.
2. The call to superclass constructor must appear as the first statement
within the subclass constructor
3. The parameters in the super call must match the order and type of
the instance variable declared in the superclass.

88. class Room {
protected int length, breadth, height;
Room(int length, int breath)
this.length = length; this.breadth = breath; }
void Room_Area()
System.out.println("The Area of the Room is:" + (length * breadth));
class HallRoom extends Room
int height;
HallRoom(int length, int breath, int height)
super(length,breath); this.height = height;
void HallRoom_Volume()
System.out.println("The Volume of the HallRoom is:" + (length *
breadth * height));

89. class MainRoom {
public static void main(String [] args)
HallRoom hr =new HallRoom(10,20,30);
hr.Room_Area();
hr.HallRoom_Volume(); }

90. //super keyword in Multilevel Inheritance
class Room {
protected int length, breadth, height;
Room(int length, int breath)
this.length = length; this.breadth = breath; }
void Room_Area()
System.out.println("The Area of the Room is:" + (length * breadth));
class HallRoom extends Room
int height;
HallRoom(int length, int breath, int height)
super(length,breath); this.height = height;
void HallRoom_Volume()
System.out.println("The Volume of the HallRoom is:" + (length * breadth *
height));

91. class BedRoom extends HallRoom{
int height_1;
BedRoom(int length, int breath, int height, int height_1)
super(length,breath,height);
this.height_1 = height_1; }
void BedRoom_Volume_1()
System.out.println("The Volume 1 of the BedRoom is:" + (length *
breadth * height * height_1));
class MainRoom
public static void main(String [] args)
BedRoom br =new BedRoom(10,20,30,40);
br.Room_Area();
br.HallRoom_Volume();
br.BedRoom_Volume_1();

92. 2. Using super to Call Superclass Method
//super keyword call Super Class Methods
class Room {
void Room_Super()
System.out.println("The Room Base is Displayed"); }
class HallRoom extends Room
void HallRoom_Intermetiate()
System.out.println("The Hall Room is Displayed");
class BedRoom extends HallRoom
void BedRoom_Sub()
super.Room_Super();
super.HallRoom_Intermetiate();
System.out.println("The Bed Room is Displayed");
class MainRoom
public static void main(String [] args)
BedRoom br = new BedRoom();
br.BedRoom_Sub();
} }

93. Inheritance
with
Method Overriding

94. 1. Method overriding in java means a subclass method overriding a super
2. Superclass method should be non-static.
3. Subclass uses extends keyword to extend the super class.
4. In the example class B is the sub class and class A is the super class.
5. In overriding methods of both subclass and superclass possess same signatures.
6. Overriding is used in modifying the methods of the super class.
7. In overriding return types and constructor parameters of methods
should match.

95. //Method Overriding
class Room {
void Room_Super()
System.out.println("The Room Base is Displayed"); }
class HallRoom extends Room
System.out.println("The Sub Class Room Base is Displayed");
class MainRoom
public static void main(String [] args)
HallRoom br = new HallRoom();
br.Room_Super();

96. Super Keyword in Method Overriding
If your method overrides one of its super class's methods, you can invoke the overridden method through the use of the keyword super. You can also use super to refer to a hidden field (although hiding fields is discouraged).
//Super keyword in Method Overriding
class Room {
void Room_Super()
System.out.println("The Room Base is Displayed"); }
class HallRoom extends Room
System.out.println("The Sub Class Room Base is Displayed");
super.Room_Super();
class MainRoom
public static void main(String [] args)
HallRoom br = new HallRoom();
br.Room_Super();

97. Inheritance with Abstract Class

98. abstract type name (parameter – list)
Abstract Class
You can require that certain methods be overridden by subclasses by specifying the abstract type modifier. These methods are sometimes referred to as subclasser responsibility because they have no implementation specified in the super class . Thus, a subclass must override them – it cannot simply use the version defined in the superclass. To declare an abstract method, use this general form:
abstract type name (parameter – list)
Any class that contains one or more abstract methods must also be declared abstract. To declare a class abstract, you simply use the abstract keyword in from of the class keyword at the beginning of the class declaration.
Conditions for the Abstract Class
1. We cannot use abstract classes to instantiate objects directly. For
example. Shape s = new Shape(); is illegal because shape is an
abstract class.
2. The abstract methods of an abstract class must be defined in its
subclass.
3. We cannot declare abstract constructors or abstract static methods.

99. //Abstract Class Implementation
abstract class A {
abstract void callme( ); // Abstract Method
void callmetoo( ) // Concrete Method
System.out.println("This is a Concrete method"); }
class B extends A
void callme( ) //Redefined for the Abstract Method
System.out.println("B's Implementation of Callme");
class MainRoom
public static void main(String [] args)
B b = new B( );
b.callme( );
b.callmetoo( );
} }

100. Inheritance with final Keyword

101. What is the purpose of final keyword?
1. Can’t initialize to variable again and again (Equivalent to Constant)
2. Can’t Method Overriding
3. Can’t Inherited
1. Can’t initialize to variable again and again (Equivalent to Constant)
class Final {
public static void main(String args[])
final int a = 45;
a = 78; //cannot assign the value to final Variable
System.out.println("The A Value is:" + a); }

102. 2. Can’t Method Overriding
class Super {
final void Super_Method()
System.out.println("This is Super Method"); }
class Sub extends Super
//Super method in sub cannot override Super_Method() in super; Overridden
//method is final
void Super_Method()
System.out.println("This is Sub Method");
class Final
public static void main(String args[])
Sub s = new Sub();
s.Super_Method();

103. 3. Can’t Inherited
final class Super {
void Super_Method()
System.out.println("This is Super Method"); }
class Sub extends Super //cannot inherit from final super
System.out.println("This is Sub Method");
class Final
public static void main(String args[])
Sub s = new Sub();
s.Super_Method();

104. Interface

105. Why are you using Interface?
1. Java does not support multiple inheritances. That is, classes in java cannot have more than one superclass. For instances,
2. a is not permitted in Java. However, the designers of java could not overlook the importance of multiple inheritances.
3. A large number of real life applications require the use of multiple inheritances whereby we inherit methods and properties from several distinct classes.
4. Since C++ like implementation of multiple inheritances proves difficult and adds complexity to the language, Java provides an alternate approach known as interfaces to support the concept of multiple inheritances.
5. Although a java class cannot be a subclass or more than one superclass, it can implement more than one interface, thereby enabling us to create classes that build upon other classes without the problems created by multiple inheritances.
class A extends B extends C { }

106. Defining Interfaces
An interface is basically a kind of class. Like classes, interfaces contain methods and variables but with major difference. The difference is that interfaces define only abstract methods and final fields. This means that interfaces do not specify any code to implement these methods and data fields contain only constants.
Syntax:
interface Interface_name {
Variable declaration;
Method declaration; }
Ex:
interface Item {
static final int code = 1001;
static final String name = “CCET”;
void display (); }
Ex:
interface Area {
final static float pi = 3.142F;
float compute (float x,float y);
void show(); }

107. How to Interface implements to the Classes
Syntax:
class class_name implements interface_name {
//Member of the Classes
//Definition of the Interfaces }
Ex:
interface student {
int slno = 12345;
String name = "CCET";
void print_details(); }
class Inter_Def implements student
void print_details()
System.out.println("The Serial Number is:" + slno);
System.out.println("The Student name is:" + name);

108. Abstract classes Interfaces
Difference between Abstract Classes and Interfaces
Abstract classes
Interfaces
Abstract classes are used only when there
is a “is-a” type of relationship between the
classes.
Interfaces can be implemented by classes
that are not related to one another.
You cannot extend more than one abstract
class.
You can implement more than one
interface.
it contains both abstract methods and non
Abstract Methods
Interface contains all abstract methods
Abstract class can implemented some
methods also.
Interfaces can not implement methods.
With abstract classes, you are grabbing
away each class’s individuality.
With Interfaces, you are merely extending
each class’s functionality.

109. Difference between Classes and Interfaces
Interface is little bit like a class... but interface is lack in instance variables....that's u can't create object for it.
Interfaces are developed to support multiple inheritances.
3. The methods present in interfaces are pure abstract.
4. The access specifiers public, private, protected are possible with classes. But the interface uses only one spcifier public
Interfaces contain only the method declarations.... no definitions
6. In Class the variable declaration as well as initialization, but interface only for initializing.

110. Types of Interfaces A B C A B C D E A B C Interface Implementation
Class
Extension A B C D E
Class
Extension
Interface
Implementation A B C
Interface
Implementation
Class

111. A B C D
Interface
Implementation
Class
Extension

112. // HIERARICHICAL INHERITANCE USING INTERFACE interface Area {
final static float pi = 3.14F;
float compute (float x,float y); }
class Rectangle implements Area
public float compute(float x,float y)
return (x * y);
class Circle implements Area
return (pi * x * x); A B C
Interface
Implementation
Class

113. class InterfaceTest {
public static void main(String args[])
Rectangle rect = new Rectangle ();
Circle cir = new Circle();
Area area; //Interface object
area = rect;
System.out.println("Area of Rectangle = " + area.compute(10,20));
area = cir;
System.out.println("Area of Circle = " + area.compute(10,0)); }

114. D //HYBRID INHERITANCE USING INTERFACES class Student {
int rollnumber;
void getnumber(int n)
rollnumber = n; }
void putnumber()
System.out.println("Roll No: " + rollnumber);
class Test extends Student
float part1, part2;
void getmarks(float m1,float m2)
part1 = m1;
part2 = m2;
void putmarks()
System.out.println("Marks obtained");
System.out.println("Part1 = " + part1);
System.out.println("Part2 = " + part2); A B C
Interface
Implementation
Class
Extension D

115. interface Sports {
float sportwt = 6.0F;
void putwt(); }
class Results extends Test implements Sports
float total;
public void putwt()
System.out.println("Sports Wt = " + sportwt);
void display()
total = part1 + part2 + sportwt;
putnumber();
putmarks();
putwt();
System.out.println("Total Score = " + total);

116. class Hybrid {
public static void main(String args[])
Results stud = new Results();
stud.getnumber(1234);
stud.getmarks(27.5F, 33.0F);
stud.display(); }

117. What is Partial Implementation?
The Interface is implementation to the Abstract class is called Partial Implementation.
Example:
interface Partial_Interface {
public void display_one(); }
abstract class Abstract_Class implements Partial_Interface
public void display_one() //Definition for the Interface Method
System.out.println("This is Interface Method");
void display_two() //Concrete Method
System.out.println("This is Concrete Method");
abstract void display_three(); //Abstract Method

118. class Pure_Class extends Abstract_Class{
void display_three() //Definition for the Abstract Method
System.out.println("This is Abstract Method"); }
class Final
public static void main(String args[])
Pure_Class pc = new Pure_Class();
pc.display_one();
pc.display_two();
pc.display_three();

119. Package

120. What is Packages?
Packages are java’s way of grouping a variety of classes and / or interfaces together. The grouping is usually done according to functionality. In fact, packages act as “containers” for classes.
What are the benefits of Packages?
1. The classes contained in the packages of other programs can be easily reused.
2. In packages, classes can be unique compared with classes in other
packages. That is, two classes in two different packages can have the same
name. They may be referred by their fully qualified name, comprising the
package name and class name.
3. Packaged provide a way to “hide classes thus preventing other programs or package from accessing classes that are meant for internal use only.
4. Packages also provide a way for separating “design” from “coding”. First we can design classes and decide their relationships, and then we can implement the java code needed for the methods. It is possible to change the implementation of any method without affecting the rest of the design.

121. Java packages are therefore classified into two types.
Types of Packages
Java packages are therefore classified into two types.
1. Pre – defined packages (Java API Packages)
2. User – defined packages
Java API Packages
Package Name
Contents
java.lang
Language support classes. These are classes that java compiler itself uses and
therefore they are automatically imported. They include classes for primitive types,
strings, math functions, threads and exceptions
java.util
Language utility classes such as vectors, hash tables, random numbers, date, etc.
java.io
Input / Output support classes. They provide facilities for the input and output of
data.
java.awt
Set of classes for implementing graphical user interface. They include classes for
windows, buttons, lists, menus and so on.
java.net
Classes for networking. They include classes for communicating with local
computers as well as with internet servers.
java.applet
Classes for creating and implementing applets.

122. 2. USER DEFINED PACKAGES How to Creating our own Packages
Creating our own package involves the following steps:
1. Declare the package at the beginning of a file using the form
package package_name;
2. Define the class that is to be put in the package and declare it public
3. Create a subdirectory under the directory where the main source files are
stored.
4. Store the listing as the classname.java file in the subdirectory created.
5. Compile the file. This creates .class file in the subdirectory.
6. The subdirectory name must match the package name exactly.
Note:
Java also supports the concept of package hierarchy. This done by specifying multiple names in a package statement, separated by dots.
Example:
package firstPackage.secondpackage;

123. Example:
Create Package:
package package1;
public class ClassA {
public void displayA()
System.out.println("Class A"); }
How to import the package:
import package1.ClassA;
class PackageTest1 {
public static void main(String args[])
ClassA objectA = new ClassA()
objectA.displayA(); }

124. ACCESS PROTECTION Access Modifier Access Location Public Protected
friendly
(default)
private protected
private
Same Class
Yes
Subclass in same package No
Other classes in same package
Subclass in other package
Non – subclasses in other packages

125. Example program for the above Access Protection Tabular
Protection.java:
package p1;
public class Protection {
int n = 1;
private int n_pri = 2;
protected int n_pro = 3;
public int n_pub = 4;
public Protection()
System.out.println("base constructor");
System.out.println("n = " + n);
System.out.println("n_pri = " + n_pri);
System.out.println("n_pro = " + n_pro);
System.out.println("n_pub = " + n_pub); }

126. This is file Derived.java:
package p1;
class Derived extends Protection {
Derived()
System.out.println("derived constructor");
System.out.println("n = " + n);
//System.out.println("n_pri = " + n_pri); //Cannot Access because //accessing level is same class //in same package
System.out.println("n_pro = " + n_pro);
System.out.println("n_pub = " + n_pub); }

127. This is file SamePackage.java:
package p1;
class SamePackage {
SamePackage()
Protection p = new Protection();
System.out.println("same package constructor");
System.out.println("n = " + p.n);
//System.out.println("n_pri = " + p.n_pri); //Cannot Access because //accessing level is same //class in same package
System.out.println("n_pro = " + p.n_pro);
System.out.println("n_pub = " + p.n_pub); }

128. This is file OtherPackage.java:
package p2;
class Protection2 extends p1.Protection {
Protection2()
System.out.println("derived other package constructor");
// System.out.println("n = " + n); //Cannot Access because //accessing level is non – sub //class same class
// System.out.println("n_pri = " + n_pri); //Cannot Access because //accessing level is same //class in same package
System.out.println("n_pro = " + n_pro);
System.out.println("n_pub = " + n_pub); }

129. This is file OtherPackage.java:
package p2;
class OtherPackage {
OtherPackage()
p1.Protection p = new p1.Protection();
System.out.println("other package constructor");
// System.out.println("n = " + p.n); // Cannot access because the // accessing level is non – sub // class in same package
// System.out.println("n_pri = " + p.n_pri); // Cannot access // because the accessing // level is same class in // same package
// System.out.println("n_pro = " + p.n_pro); // Cannot access // because the accessing // level is sub – class in // other package
System.out.println("n_pub = " + p.n_pub); }

130. String functions

131. SPECIAL STRING OPERATIONS
1. Automatic creation of new String instances from string literals.
2. Concatenation of multiple String object by used of the + operators
3. Conversion of other data types to a string representation.
String Literals
class String_Operation {
public static void main(String args[])
char chars [ ] = {'a', 'b', 'c'};
String s1 = new String(chars);
String s2 = "Chettinad"; //Use String Literals, Java automatically
//constructs a String object
System.out.println("The Displayed String_1 is:" + s1);
System.out.println("The Displayed String_2 is:" + s2);
System.out.println("The Length of the String is: " +
"Chettinad".length()); }

132. 2. String Concatenation
class String_Operation {
public static void main(String args[])
String age = " 9 ";
String s = "He is" + age + "Years old."; //Java does not allow ( // )operators to be // applied to String // objects.
System.out.println(s); }

133. 3. String Concatenation with Other Data Types
class String_Operation {
public static void main(String args[])
int age = 9;
String s1 = "He is " + age + " Years old. "; // The int value in age is // automatically // converted into its string // representation within a //String object.
System.out.println(s1);
String s2 = "four: " ;
System.out.println(s2);
String s3 = "four: " + (2 + 2);
System.out.println(s3); }

134. 4. String Conversion and toString()
To implement toString(), simply return a String object that contains the human readable string.
class Box {
double width;
double height;
double depth;
Box(double w,double h,double d)
width = w;
height = h;
depth = d; }
public String toString()
return "Dimensions are " + width + " by " + depth + " by " + height + ".";

135. class String_Operation{
public static void main(String args[])
Box b = new Box(10, 12, 14);
String s = "Box b: " + b; // Concatenate Box object
System.out.println(b);
System.out.println(s); }

136. CHARACTER EXTRACTION
The String class provides a number of ways in which characters can be extracted form a String object. That is Character Extraction.
charAt()
Syntax:
char charAt(int where)
class String_Operation {
public static void main(String args[ ])
char ch;
ch = "Chettinad".charAt(4);
System.out.println("The 4 Character is:" + ch); }

137. 2. getChars()
If you need to extract more than one character at a time, you can use the getChars() method.
Syntax:
void getChars(int sourceStart,int sourceEnd,char target [ ],int targetStart)
class String_Operation {
public static void main(String args[])
String s = "This is a demo of the getChars method.";
int start = 10;
int end = 14;
char buf [ ] = new char[end - start];
s.getChars(start,end,buf,0);
System.out.println(buf); }

138. 3. getBytes()
There is an alternative to getChars() that stores the character in an array of bytes. This method is called getBytes(), and it uses the default character-to-byte conversions provided by the platform.
Here is its simplest form:
byte [] getBytes();
Other forms of getBytes are also available. getBytes is most useful when you are exporting a String value into an environment that does not support 16 - bit unicode character. For example, most Internet protocols and text file formats use 8 - bit ASCII for all text interchage.
class String_Operation {
public static void main(String args[])
String msg="HelloWorld";
byte b[ ]=msg.getBytes();
System.out.println("The Character in array of Bytes is: " + b); }

139. 4. toCharArray()
If you want to convert all the characters in a String object into a character array, the easiest way is to call toCharArray(). It returns an array of characters for the entire string.
It has this general form:
char [ ] toCharArray()
This function is provided as a convenience, since it is possible to use getChars() to achieve the same result.
class String_Operation {
public static void main(String args[])
String str = "einstein relativity concept is still a concept of great discussion";
char heram[ ] = str.toCharArray();
System.out.print("Converted value from String to char array is: ");
System.out.println(heram); }

140. STRING COMPARISON equals() and equalsIgnoreCase()
To compare two strings for equality, use equals()
Syntax:
boolean equals(Object str)
Here, str is the String object being compared with the invoking String object. It returns true if the strings contain the same characters in the same order, and false otherwise. The comparison is case - sensitive.
To perform a comparison that ignores case differences, call equalsIgnoreCase(). When it compares two string, it considers A - Z to be the same as a - z.
boolean equalsIgnoreCase(String str)
Here, str is the String object being compared with the invoking String object. It, too, returns true if the strings contain the same characters in the same order, and false otherwise.

141. class String_Operation{
public static void main(String args[])
String s1 = "Hello";
String s2 = "Hello";
String s3 = "Good - Bye";
String s4 = "HELLO";
System.out.println(s1 + " equals " + s2 + " -> " + s1.equals(s2));
System.out.println(s1 + " equals " + s3 + " -> " + s1.equals(s3));
System.out.println(s1 + " equals " + s4 + " -> " + s1.equals(s4));
System.out.println(s1 + " equalsIgnoreCase " + s4 + " -> " s1.equalsIgnoreCase(s4)); }

142. 2. regionMatches()
The regionMatches() method compares a specific region inside a string with another specific region in another string. There is an overloaded form that allows you to ignore case in such comparisions
Syntax:
boolean regionMatches(int startIndex,String str2,int str2StartIndex,int
numChars)
boolean regionMatches(boolena ignorCase,int startIndex,String str2,int
strStrartIndex,int numChars)

143. class String_Operation{
public static void main(String args[])
String str1 = new String("Java is a wonderful language");
String str2 = new String("It is an object-oriented language");
boolean result = str1.regionMatches(20, str2, 25, 0);
System.out.println(result); }
class String_Operation {
public static void main(String args[])
String str1 = new String("Java is a wonderful language");
String str2 = new String("It is an object-oriented language");
boolean result = str1.regionMatches(true, 20, str2, 25, 0);
System.out.println(result); }

144. 3. startsWith() and endsWith()
The startsWith() method determines whether a given String begins with a specified string.
The endsWith() method determines whether the String in questions ends with a specified string.
Syntax:
boolean startsWith(String str)
boolean endsWith(String str)
str is the String object being tested. If the string matches, true is returned. Otherwise false is returned
class String_Operation {
public static void main(String args[])
boolean a, b;
a = "Chettinad".startsWith("Chi");
b = "Chettinad".endsWith("nad");
System.out.println("The Start of the String is: " + a);
System.out.println("The Ends of the String is:" + b); }

145. 4. equals() Versus ==
The equals function and == operator are perform two different operations
The equals() method compares the characters inside a String object.
The == operator compares two object references to see whether they refer to the same instance.
class String_Operation {
public static void main(String args[])
String s1 = "Hello1234";
String s2 = new String(s1);
System.out.println(s1 + " equals " + s2 + " -> " + s1.equals(s2));
System.out.println(s1 + " == " + s2 + " -> " + (s1 == s2)); }
The Contents of the two String objects are identical, but they are distinct object, This means that s1 and s2 do not refer to the same objects.

146. 5. compareTo()
Syntax:
int compareTo(String str);
Value Meaning
Less than zero The invoking string is less than str.
Greater than zero The invoking string greater than str.
Zero The two strings are equal.

147. class String_Operation{
public static void main(String args[])
String s1 = "Chettinad";
String s2 = "Chettinad";
int n = s1.compareTo(s2);
if (n==0)
System.out.println("The Two String are Equal");
else if(n>0)
System.out.println("The First Strings is Greater than the
Second String");
else if(n<0)
System.out.println("The First String is Smaller than the }

148. MODIFYING A STRING substring() substring() has tow forms.
1. String substring(int startIndex)
2. String substring(int startIndex,int endIndex)
class String_Operation {
public static void main(String args[ ])
String s1 = "This is a test. This is, too.";
String s2 = s1.substring(5);
String s3 = s1.substring(5,8);
System.out.println("The Sub String of S2 is: " + s2);
System.out.println("The Sub String of S3 is: " + s3); }

149. 2. concat()
You can concatenate two strings using concat()
Syntax:
String concat(String str);
class String_Operation {
public static void main(String args[ ])
String s1 = "One";
String s2 = s1.concat(" Two");
System.out.println("The Concatenation of Two String is: " + s2); }

150. String replace(char original, char replacement)
The replace() method replaces all occurences of one character in the invoking string with another character.
Syntax:
String replace(char original, char replacement)
class String_Operation {
public static void main(String args[ ])
String s = "Hello".replace('l','w');
System.out.println("The Replacement of the String is:" + s); }
4. trim()
The trim() method returns a copy of the invoking string from which any leading and trailing whitespace has been removed.
Syntax:
String trim()
class String_Operation {
public static void main(String args[ ])
String s = " Hello world ".trim();
System.out.println("The Removable Whitspace of the String is: " + s); }

151. StringBuffer Functions
StringBuffer is a peer class of String that provides much of the functionality of strings.
2. String Buffer represents growable and writeable character sequences.
3. String Buffer may have characters and substrings inserted in the middle or appended
to the end.
4. String Buffer will automatically grow to make room for such additions and often has
more characters preallocated than are actually needed, to allow room for growth.
StringBuffer Constructors
StringBuffer defined these three constructors:
1. StringBuffer()
2. StringBuffer(int size)
3. StringBuffer(String str)

152. (1) The default constructor reserves room for 16 characters without reallocation.
(2) The second version accepts an integer argument that explicitly sets the size of
the buffer.
(3) The third version accepts a String argument that sets the initial contents of the
StringBuffer object and reserves room for 16 more characters without reallocation.
length() and capacity()
Syntax:
int length()
int capacity()
class String_Operation {
public static void main(String args[ ])
StringBuffer sb = new StringBuffer("Hello");
System.out.println("Buffer = " + sb);
System.out.println("Length = " + sb.length());
System.out.println("Capacity = " + sb.capacity()); //Its capacity is 21
//because room for 16 additional characters is automatically added. }

153. 2. ensureCapacity()
1. If you want to preallocate room for a certain number of characters after a StringBuffer has been constructed, you can use ensureCapacity() to set the size of the buffer.
2. This is useful if you know in advance that you will be appending a large number of small strings to a StringBuffer.ensureCapacity() has this general form:
void ensureCapacity(int capacity);
Here, capacity specifies the size of the buffer.
class String_Operation {
public static void main(String args[])
StringBuffer sb = new StringBuffer("Rose India");
//Returns the current capacity of the String buffer.
System.out.println("Buffer : "+sb+"\nCapacity : " + sb.capacity());
//Increases the capacity, as needed, to the specified amount in the
//given string buffer object
sb.ensureCapacity(27);
System.out.println("New Capacity = " + sb.capacity()); }

154. 3. setLength()
To set the length of the buffer within a StringBuffer object, use setLength().
Syntax:
void setLength(int len)
Here, len specifies the length of the buffer. This value must be non - negative.
when you increase the size of the buffer, null characters are added to the end of the existing buffer.
class String_Operation {
public static void main(String[ ] args)
// Construct a StringBuffer object:
StringBuffer s = new StringBuffer("Hello world!");
// Change the length of buffer to 5 characters:
s.setLength(5);
System.out.println(s); }

155. 4. charAt() and setCharAt()
1. The value of a single character can be obtained from a StringBuffer via the charAt() method.
Syntax:
char charAt(int where)
For charAt(), where specifies the index of the character being obtained.
2. You can set the value of a character within a StringBuffer using setCharAt().
void setCharAt(int where,char ch)
For setCharAt(), where specifies the index of the character being set, and ch specifies the new value of that character.
For both methods, where must be nonnegative and must not specify a location beyond the end of the buffer.

156. class String_Operation{
public static void main(String args[])
StringBuffer sb = new StringBuffer("Hello");
System.out.println("Buffer before = " + sb);
System.out.println("charAt (1) before = " + sb.charAt(1));
sb.setCharAt(1,'i');
sb.setLength(2);
System.out.println("Buffer after = " + sb);
System.out.println("charAt(1) after = " + sb.charAt(1)); }

157. 5. getChars()
To copy a substring of a StringBuffer into an array, use the getChars() method.
Syntax:
void getChars(int sourceStart,int sourceEnd,char target[],int
targetStart);
class String_Operation {
public static void main(String[] args)
// Construct a StringBuffer object:
StringBuffer src = new StringBuffer("To learn JAVA, start with keywords.");
// Declare a new char array:
char[] dst = new char[2];
// Copy the chars #9 and #10 to dst:
src.getChars(9,11,dst,0);
// Display dst:
System.out.println(dst); }

158. 3. Here are a few of its forms: StringBuffer append(String str)
1. The append() method concatenates the string representation of any other type of data ot the end of the invoking StringBuffer object.
2. It has overloaded versions for all the built - in types and for Object.
3. Here are a few of its forms:
StringBuffer append(String str)
StringBuffer append(int num)
StringBuffer append(Object obj)
4. String.valueOf() is called for each parameter to obtain its string representation.
5. The result is appended to the current StringBuffer object. The buffer itself is returned by each version of append().
StringBuff append(String str)
public class String_Operation {
public static void main(String[] args)
// Construct a String object:
String s1 = new String("3.14");
// Construct a StringBuffer object:
StringBuffer s = new StringBuffer("The ratio is: ");
// Append the string and display the buffer:
System.out.println(s.append(s1) + "."); }

159. StringBuffer append(int num)
class String_Operation {
public static void main(String args[])
String s;
int a = 42;
StringBuffer sb = new StringBuffer(40);
s = sb.append("a = ").append(a).append("!").toString();
System.out.println(s); }
StringBuffer append(Object obj)
/*class String_Operation {
public static void main(String[] args)
// Declare and initialize an object:
Object d = new Double(3.14);
// Construct a StringBuffer object:
StringBuffer s = new StringBuffer("The ratio is: ");
// Append the object and display the buffer:
System.out.println(s.append(d) + "."); }

160. 1. The insert() method inserts one string into another.
2. It is overloaded to accept values of all the simple types, plus Strings and Objects.
3. Like append(), it calls String.valueOf() to obtain the string representation of the value it is called with.
4. These are a few of its forms:
StringBuffer insert(int index,String str)
StringBuffer insert(int index,char ch)
StringBuffer insert(int index, object obj)
Here, index specifies the index at which point the string will be inserted into the invoking StringBuffer object.
StringBuffer insert(int index,String str)
class String_Operation {
public static void main(String[] args)
// Construct a StringBuffer object:
StringBuffer buf = new StringBuffer("Hello !");
// Construct a String object:
String s = new String("there");
// Insert the string "s" at offset 6:
buf = buf.insert(6,s);
// Display the buffer:
System.out.println(buf); }

161. StringBuffer insert(int index,char ch)
public class String_Operation {
public static void main(String[] args)
// Construct a StringBuffer object:
StringBuffer buf = new StringBuffer("Hello #!");
// Insert 'J' at the offset 6:
buf = buf.insert(6,'J');
// Display the buffer:
System.out.println(buf); }
StringBuffer insert(int index, object obj)
class String_Operation {
public static void main(String[] args)
// Construct a StringBuffer object:
StringBuffer buf = new StringBuffer("Hello !");
// Construct an object:
Object d = new Double(3.45);
// Insert d at the offset 6:
buf = buf.insert(6,d);
// Display the buffer:
System.out.println(buf);
} }

162. 8. reverse()
You can reverse the character within s StringBuffer object using reversed().
Syntax:
StringBuffer reverse()
class String_Operation {
public static void main(String args[])
StringBuffer s = new StringBuffer("abcdef");
System.out.println(s);
s.reverse(); }

163. 9. delete() and deleteCharAt()
StringBuffer the ability to delete characters using the methods delete() and deleteCharAt().
Syntax:
StringBuffer delete(int startIndex, int endIndex)
StringBuffer deleteCharAt(int loc)
class String_Operation {
public static void main(String args[])
StringBuffer sb = new StringBuffer("This is a Test.");
sb.delete(4,7);
System.out.println("After delete: " + sb);
sb.deleteCharAt(0);
System.out.println("After deleteCharAt: " + sb); }

164. 10. replace()
It replace one set of character with another set inside a StringBuffer object.
StringBuffer replace(int startIndex, int endIndex, String str);
class String_Operation {
public static void main(String args[])
StringBuffer sb = new StringBuffer("This is a test.");
sb.replace(5,7, "was");
System.out.println("After Replace: " + sb); }

165. 11. substring()
Syntax:
String substring(int startIndex)
String substring(int startIndex,int endIndex)
class String_Operation {
public static void main(String args[])
StringBuffer sb = new StringBuffer("Chettinad");
sb.substring(6);
System.out.println("The Substring is: " + sb);
sb.substring(2,5); }

166. UNIT – III
Balance Chapters

167. THE CHARACTER STREAMS

168. The character Streams
While the byte stream classes provide sufficient functionality to handle any type of I/O operation, they cannot work directly with Unicode characters.
Since one of the main purposes of Java is to support the “write once, run anywhere” philosophy, it was necessary to include direct I/O support for characters.
At the top of the character stream hierarchies are the Reader and Writer abstract classes.
Reader
Reader is an abstract class that defines java’s model of streaming character input. All of the methods in this class will throw an IOException on error conditions.
Writer
Writer is an abstract class that defines streaming character output . All of the methods in this class return a void value and throw an IOException in the case of errors.

169. The Methods Defined by Reader
Description
abstract void close()
Closes the input source. Further read attempts will generate an IOException.
void mark(int numChars)
Places a mark at the current point in the input stream that will remain valid until numChars characters are read
boolean markSupported()
Returns true if mark() / reset() are supported on this stream
int read()
Returns an integer representation of the next available character from the invoking input stream. -1 is returned when the end of the file is encountered.
int read(char buffer[])
Attempts to read up to buffer.length characters into buffer and returns the actual number of character that were successfully read. -1 is returned when the end of the file encountered.
abstract int read(
char buffer[],
int offset,
int numChars)
Attempts to read up to numChars characters into buffer starting at buffer[offset], returning the number of characters successfully read. -1 is returned when the end of the file is encountered.

170. Method
Description
boolean ready()
Returns true if the next input request will not wait. Otherwise, it returns false.
void reset()
Resets the input pointer to the previously set mark
long skip(
long numChars)
Skips over numChars characters of input , returning the number of characters actually skipped.

171. The Methods Defined by Writer
Description
abstract void close()
Closes the output stream. Further write attempts will generate an IOException.
abstract void flush()
Finalizes the output state so that any buffers are cleared. That is, it flushes the output buffers.
void write (int ch)
Writes a single character to the invoking output stream. Note that the parameter is an int, which allows you to call write with expressions without having to cast them back to char.
void write(char buffer[])
Writes a complete array of characters to the invoking output stream.
abstract void write(
char buffer[],
int numChars)
Writes a subrange of numChars characters from the array buffer, beginning at buffer[offset] to the invoking output stream.
void write(String str)
Writes str to the invoking output stream.
void write(String str,
int offset,
Writes a subrange of numChars characters from the array str, beginning at the specified offset.

172. FileReader
The FileReader class creates a Reader that you can use to read the contents of a file. Its most commonly used constructors are shown here:
FileReader (String filePath)
FileReader (File filObj)
Note:
Either can throw a FileNotFoundException. Here, filePath is the full path name of a file and fileobj is a File object that describes the file.

173. import java.io.*;
class FileReaderDemo {
public static void main(String args[]) throws IOException
FileReader fr = new FileReader("FileReaderDemo.java");
BufferedReader br = new BufferedReader(fr);
String s;
while((s = br.readLine()) != null)
System.out.println(s); }
fr.close();

174. FileWriter
The FileWriter class creates a Writer that you can use to writet to a file. Its most commonly used constructors are shown here:
FileWriter(String filePath)
FileWriter(String filePath, boolean append)
FileWriter(File fileObj)
FileWriter(File fileObj, boolean append)
They can throw an IOException. Here, filePath is the full path name of a file, and fileObj is a File Object that describes the file. If append is true, then output is appended to the end fo the file.

175. import java.io.*;
class FileWriterDemo {
public static void main(String args[])
try
// Create file
FileWriter fstream = new FileWriter("out.txt");
BufferedWriter out = new BufferedWriter(fstream);
out.write("Hello Java");
//Close the output stream
out.close(); }
catch (Exception e)
//Catch exception if any
System.err.println("Error: " + e.getMessage());

176. CharArrayReader
CharArrayReader is an implementation of an input stram that uses a character array as the source. The class has two constructos, each of which requires a character array to provide the data source:
CharArrayReader(char arrray[])
CharArrayReader(char array[],int start,int numChars)
Here, array is the input source. The second constructor creates a Reader from a subset of your character array that begins with the character at the index specified by start and is numChars long.

177. import java.io.*;
class CharArrayReaderDemo {
public static void main(String args[]) throws IOException
String tmp = "abcdefghijklmnopqrstuvwxyz";
int length = tmp.length();
char c[] = new char[length];
tmp.getChars(0, length, c, 0);
CharArrayReader input1 = new CharArrayReader(c);
CharArrayReader input2 = new CharArrayReader(c, 0, 5);
int i;
System.out.println("input1 is:");
while((i = input1.read()) != -1)
System.out.print((char)i); }
System.out.println();
System.out.println("input2 is:");
while((i = input2.read()) != -1)

178. CharArrayWriter(int numChars)
CharArrayWriter is an implementation of an output stram that uses a character array as the destination. The class has two constructos, each of which requires a character array to provide the data destination:
CharArrayWriter()
CharArrayWriter(int numChars)
In the first form, a buffer with a default size is created. In the second, a buffer is created with a size equal to that specified by numChars. The buffer is held in the buf field of CharArrayWriter. The buffer size will be increased automatically, if needed. The number of characters held by the buffer is contained in the count field of CharArrayWriter. Both buf and count are protected fields.

179. import java.io.*;
class CharArrayWriterDemo {
public static void main(String args[]) throws IOException
CharArrayWriter f = new CharArrayWriter();
String s = "This should end up in the array";
char buf[] = new char[s.length()];
s.getChars(0, s.length(), buf, 0);
f.write(buf);
System.out.println("Buffer as a string");
System.out.println(f.toString());
System.out.println("Into array");
char c[] = f.toCharArray();
for (int i=0; i<c.length; i++)
System.out.print(c[i]); }
System.out.println("\nTo a FileWriter()");
FileWriter f2 = new FileWriter("test.txt");
f.writeTo(f2);
f2.close();
System.out.println("Doing a reset");
f.reset();
for (int i=0; i<3; i++)
f.write('X');
} }

180. BufferedReader
BufferedReader improves performance by buffering input. It has two constructors:
BufferedReader(Reader inputStream)
BufferedReader(Reader inputStream,int bufsize)
The first form creates a buffered character stream using a default buffer size. In the second, the size of the buffer is passed in bufsize.

181. import java.io.*;
class BufferedReaderDemo {
public static void main(String args[]) throws IOException
String s = "This is a © copyright symbol " + "but this is &copy not.\n";
char buf[] = new char[s.length()];
s.getChars(0, s.length(), buf, 0);
CharArrayReader in = new CharArrayReader(buf);
BufferedReader f = new BufferedReader(in);
int c;
while((c = f.read()) != -1)
System.out.print((char)c); }

182. BufferedWriter
A BufferedWriter is a Writer that adds a flush() method that can be used to ensure that data buffers are physically wirtten to the actual output stream. Using a BufferedWriter can increase performance by reducing the number of times data is actually physically written to the output stream. A BufferedWriter has these two constructors:
BufferedWriter(Writer outputStream)
BufferedWriter(Writer outputStream,int bufsize)
The first form creates a buffered character stream using a default buffer size. In the second, the size of the buffer is passed in bufsize.

183. import java.io.*;
class BufferedWriterDemo {
public static void main(String args[]) throws Exception
// Create a new instance of a BufferedWriter object using a StringWriter.
StringWriter sw = new StringWriter();
BufferedWriter bw = new BufferedWriter(sw);
// Write to the underlying StringWriter.
String str = new String("This is the string being written.");
// Print out the 6 characters.
bw.write(str, 12, 6);
bw.flush();
System.out.println(sw.getBuffer());
// Close the BufferedWriter object and the underlying StringWriter object.
sw.close();
bw.close(); }

184. PushbackReader
The PushbackReader class allows one or more characters to be returned to the input stream. This allows you to look ahead in the input stream. Here are its two constructors:
PushbackReader(Reader inputStream)
PushbackReader(Reader inputStream,int bufSize)
The first form creates a buffered stream that allows one character to be pushed back. In the second, the size of the pushback buffer is passed in bufSize.
PushbackReader provides unread(), which returns one or more characters to the invoking input stream. It has the three forms shown here:
void unread(int ch)
void unread(char buffer[])
void unread(char buffer[], int offset, int numChars)
The first form pushes back the character passed in ch. This will be the next character returned by a subsequent call to read(). The second form returns the characters in buffer. The third form pushes back numChars characters beginning at offset from buffer. An IOException will be thrown if there is an attempt to return a character when the pushback buffer is full.

185. import java.io.*;
class PushbackReaderDemo {
public static void main(String args[]) throws IOException
String s = "if (a == 4) a = 0 ; \\n";
char buf[] = new char[s.length()];
s.getChars(0, s.length(), buf, 0);
CharArrayReader in = new CharArrayReader(buf);
PushbackReader f = new PushbackReader(in);
int c;
while ((c = f.read()) != -1)
switch(c)
case '=':
if ((c = f.read()) == '=')
System.out.print(".eq.");
else
System.out.print("<-");
f.unread(c); }
break;
default:
System.out.print((char) c);
} } }

186. PrintWriter
PrintWriter is essentially a character – oriented version of PrintStream. It provides the formatted output methods print() and println(). PrintWriter has four constructors:
PrintWriter(OutputStream outputStream)
PrintWriter(OutputStream outputStream, boolean flushOnNewline)
PrintWriter(Writer outputStream)
PrintWriter(Writer outputStream, boolean flushOnNewline)
Where flushOnNewline controls whether Java flushes the output stream every time println() is called. If flushOnNewline is true, flushing automatically takes place. If false, flushing is not automatic. The first and third constructors do not automatically flush.

187. import java.io.*;
class PrintWriterDemo {
public static void main(String args[])
PrintWriter pw = new PrintWriter(System.out, true);
pw.println("This is a string");
int i = -7;
pw.println(i);
double d = 4.5e-7;
pw.println(d); }

188. SERIALIZATION

189. Serialization
Serialization is the process of writing the state of an object to a byte stream.
This is useful when you want to save the state of your program to a persistent storage area, such as a file.
At a later time, you may restore these objects by using the process of deserialization.
Serialization is also needed to implement Remote Method Invocation (RMI).
RMI allows a Java object on one machine to invoke a method of a Java object on a different machine.
An object may be supplied as an argument to that remote method.
The sending machine serializes the object and transmits it.
The receiving machine deserializes it.

190. void writeExternal(ObjectOutput outStream) throws IOException
Serializable
Only an object that implements the Serializable interface can be saved and restored by the serialization facilities.
The Serializable interface defines no members. It is simply used to indicate that a class may be serialized.
If a class is serializable, all of its subclasses are also serializable.
Variables that are declared as transient are not saved by the serialization facilities.
Also static variable are not saved.
Externalizable
The Java facilities for serialization and deserialization have been designed so that much of the work to save and restore the state of an object occurs automatically.
However, there are cases in which the programmer may need to have control over these processes.
For example, it may be desirable to use compression or encryption techniques. The Externalizable interface is designed for these situations.
The Externalizable interface defines these two methods:
void readExternal(ObjectInput inStream) throws IOException, ClassNotFoundException
void writeExternal(ObjectOutput outStream) throws IOException
In these methods, inStream is the byte stream from which the object is to be read, and outStream is the byte stream to which the object is to be written.

191. ObjectOutput
The ObjectOutput interface extends the DataOutput interface and support object Serialization. The following Methods is called the serialize an object. All of these methods will throw an IOException on error condition.
Method
Description
void close()
Closes the invoking stream. Further write attempts will generate an IOException.
void flush()
Finalizes the output state so that any buffers are cleared. That is, it flushes the output buffers.
void wirte(byte buffer[])
Writes an array of bytes to the invoking stream.
void write(byte buffer[], int offset, int numBytes)
Writes a subrange of numBytes bytes from the array buffer, beginning at buffer[offset].
void write(int b)
Writes a single byte to the invoking stream. The byte written is the low – order byte of b.
Void writeObject(Object obj)
Writes object obj to the invoking stream.

192. ObjectOutputStream(OutputStream outStream) throws IOException
The ObjectOutputStream class extends the OutputStream class and implements the ObjectOutput interface. It is responsible for writing objects to a stream. A constructor of this class is:
ObjectOutputStream(OutputStream outStream) throws IOException
The argument outStream is the output stream to which serialized objects will be written.
Method
Description
void close()
Closes the invoking stream. Further write attempts will generate an IOException.
void flush()
Finalizes the output state so that any buffers are cleared. That is, it flushes the output buffers.
void wirte(byte buffer[])
Writes an array of bytes to the invoking stream.
void write(byte buffer[], int offset, int numBytes)
Writes a subrange of numBytes bytes from the array buffer, beginning at buffer[offset].
void write(int b)
Writes a single byte to the invoking stream. The byte written is the low – order byte of b.
void writeBoolean(boolean b)
Writes boolean to the invoking stream.

193. Method
Description
void writeByte(int b)
Writes a byte to the invoking stream. The byte written is the low – order byte of b.
void writeBytes(String str)
Writes the bytes representing str to the invoking stream.
void writeChar(int c)
Writes a char to the invoking stream.
void writeChars(String str)
Writes the characters in str to the invoking stream.
void writeDouble(double d)
Writes a double to the invoking stream.
void writeFloat(float f)
Writes a float to the invoking stream.
void writeInt(int i)
Writes a int to the invoking stream.
void WriteShort(int i)
Writes a short to the invoking stream.
void writeLong(long i)
Writes a long to the invoking stream.
final void writeObject(Object obj)
Writes a obj to the invoking stream.

194. ObjectInput
The ObjectInput interface extends the DataInput interface and support object Serialization. The following Methods is called the serialize an object. All of these methods will throw an IOException on error condition.
Method
Description
int available()
Returns the number of bytes that are now available in the input buffer.
void close()
Closes the invoking stream. Further read attempts will generate an IOException.
int read()
Returns an integer representation of the next available byte of input. -1 is returned when the end of the file is encountered.
int read(byte buffer[])
Attempts to read up to buffer length bytes into buffer, returning the number of bytes that were successfully read. -1 is returned when the end of the file is encountered.
int read(byte buffer[], int offset, int numBytes)
Attempts to read up to numBytes bytes into buffer starting at buffer[offset], returning the number of bytes that were successfully read. -1 is returned when the end of the file is encountered.

195. ObjectInputStream Method Description Object readObject()
Reads an object from the invoking stream.
Long skip(long numBytes)
Ignores(that is, skips) numBytes bytes in the invoking stream, returnign the number of bytes actually ignored.
ObjectInputStream
The ObjectInputStream class extends the InputStream class and implements the ObjectInput interface. It is responsible for Reading objects from a stream. A constructor of this class is:
ObjectInputStream(InputStream inStream) throws IOException,
StreamCorruptedException
The argument inStream is the input stream from which serialized objects should be read.

196. Method
Description
int available()
Returns the number of bytes that are now available in the input buffer.
void close()
Closes the invoking stream. Further read attempts will generate an IOException
int read()
Returns an integer representation of the next available byte of input. -1 is returned when the end of the file is encountered.
int read(byte buffer[],int offset,int numBytes)
Attempts to read up to numBytes bytes into buffer starting at buffer[offset], returning the number of bytes successfully read. -1 is returned when the end of the file is encountered.
boolean readBoolena()
Reads and returns boolean from the invoking stream.
byte readByte()
Reads and returns a byte from the invoking stream.
char readChar()
Reads and returns a char from the invoking stream.
double readDouble()
Reads and returns a double from the invoking stream.
float readFloat()
Reads and returns a float from the invoking stream.
void readFully(byte buffer[])
Reads buffer length bytes into buffer. Returns only when all bytes have been read.
void readFully(byte buffer[], int offset, int numBytes)
Reads numBytes bytes into buffer starting at buffer[offset]. Returns only when numBytes have been read.

197. Method
Description
int readInt()
Reads and returns an int from the invoking stream.
long readLong()
Reads and returns a long from the invoking stream.
final Object readObject()
Reads and returns an object from the invoking stream.
short readShort()
Reads and returns a short from the invoking stream.
int readUnsignedByte()
Reads and returns an unsigned byte from the invoking stream.
int readUnsignedShort()
Reads an unsigned short from the invoking stream.

198. import java.io.*;
class SerializationDemo {
public static void main(String arg[])
//Object Serialization
try
MyClass object1 = new MyClass("Hello", -7,2.7e10);
System.out.println("Object1: " + object1);
FileOutputStream fos = new FileOutputStream("serial");
ObjectOutputStream oos = new ObjectOutputStream(fos);
oos.writeObject(object1);
oos.flush();
oos.close(); }
catch(Exception e)
System.out.println("Exception during serialization: " + e);
System.exit(0);

199. //Object Deserialization
try {
MyClass object2;
FileInputStream fis = new FileInputStream("serial");
ObjectInputStream ois = new ObjectInputStream(fis);
object2 = (MyClass)ois.readObject();
ois.close();
System.out.println("object2: " + object2); }
catch(Exception e)
System.out.println("Exception during deserialization: " + e);
System.exit(0);
class MyClass implements Serializable
String s;
int i;
double d;
public MyClass(String s,int i,double d)
this.s = s;
this.i = i;
this.d = d;
public String toString()
return "S=" + s + "; i=" + i + "; d=" + d;
} }

200. Constructor Calling Conversion Action Method Calling Conversion Action
Converting Primitive Numbers to Object Numbers using Constructor Methods
Constructor Calling
Conversion Action
Integer intval = new Integer(i)
Primitive integer to Integer object
Float floatval = new Float(f)
Primitive float to Float object
Double doubleval = new Double(d)
Primitive double to Double object
Long longval = new Long(l)
Primitive long to Long object
Converting Object Numbers to Primitive Numbers using typeValue() method
Method Calling
Conversion Action
int i = IntVal.intValue()
Object to Primitive integer
float f = FloatVal.floatValue()
Object to Primitive float
long l = LongVal.longValue()
Object to Primitive long
double d = DoubleVal.doubleValue()
Object to Primitive double

201. Constructor Calling Conversion Action Method Calling Conversion Action
Converting Numbers to Strings Using a String( ) Method
Constructor Calling
Conversion Action
str = Integer.toString(i)
Primitive Integer to string
str = Float.toString(f)
Primitive float to string
str = Double.toString(d)
Primitive double to string
str = Long.toString(l)
Primitive long to string
Converting String Objects to Numeric Object Using the Static Method ValueOf()
Method Calling
Conversion Action
DoubleVal = Double.ValueOf(str)
Converts String to Double object
FloatVal = Float.ValueOf(str)
Converts String to Float object
IntVal = Integer.ValueOf(str)
Converts string to Integer object
LongVal = Long.Valueof(str)
Converts string to Long object

202. Constructor Calling Conversion Action
Converting Numberic Strings to Primitive Numbers Using Parsing Methods
Constructor Calling
Conversion Action
int i = Integer.parseInt(str)
Converts String to Primitive Integer
long l = Long.parseLong(str)
Converts String to Primitive long

203. UNIT - V

204. StringTokenizer
The processing of text often consists of parsing a formatted input string.
Parsing is the division of text into a set of discrete parts, or tokens, which in a certain sequence can convey a semantic meaning.
The StringTokenizer class provides the first step in this parsing process, often called the lexer (lexical analyzer) or scanner.
StringTokenizer implements the Enumeration interface.
Therefore, given an input string, you can enumerate the individual tokens contained in it using StringTokenizer.
To use StringTokenizer, you specify an input string and a string that contains delimiters.
Delimiters are characters that separate tokens.
Each character in the delimiters string is considered a valid delimiter—for example, “,;:” sets the delimiters to a comma, semicolon, and colon.
The default set of delimiters consists of the whitespace characters: space, tab, newline, and carriage return.
The StringTokenizer constructors are shown here:
StringTokenizer(String str)
StringTokenizer(String str, String delimiters)
StringTokenizer(String str, String delimiters, boolean delimAsToken)

206. import java.util.StringTokenizer;
class STDemo {
static String in = "title=Java: The Complete Reference;" +
"author=Schildt;" + "publisher=Osborne/McGraw-Hill;" +
"copyright=2002";
public static void main(String args[])
StringTokenizer st = new StringTokenizer(in, "=;");
while(st.hasMoreTokens())
String key = st.nextToken();
String val = st.nextToken();
System.out.println(key + "\t" + val); }

207. BitSet
A BitSet class creates a special type of array that holds bit values. This array can increase in size as needed. This makes it similar to a vector of bits. The BitSet constructors are shown here:
The first version creates a default object. The second version allows you to specify its initial size (that is, the number of bits that it can hold). All bits are initialized to zero. BitSet implements the Cloneable interface and defines the methods.
BitSet( )
BitSet(int size)

210. // BitSet Demonstration.
import java.util.BitSet;
class BitSetDemo {
public static void main(String args[])
BitSet bits1 = new BitSet(16);
BitSet bits2 = new BitSet(16);
// set some bits
for(int i=0; i<16; i++)
if((i%2) == 0) bits1.set(i);
if((i%5) != 0) bits2.set(i); }
System.out.println("Initial pattern in bits1: ");
System.out.println(bits1);
System.out.println("\nInitial pattern in bits2: ");
System.out.println(bits2);
// AND bits
bits2.and(bits1);
System.out.println("\nbits2 AND bits1: ");
// OR bits
bits2.or(bits1);
System.out.println("\nbits2 OR bits1: ");
// XOR bits
bits2.xor(bits1);
System.out.println("\nbits2 XOR bits1: ");

211. Calendar
The abstract Calendar class provides a set of methods that allows you to convert a time in milliseconds to a number of useful components.
Some examples of the type of information that can be provided are: year, month, day, hour, minute, and second.
It is intended that subclasses of Calendar will provide the specific functionality to interpret time information according to their own rules.
This is one aspect of the Java class library that enables you to write programs that can operate in several international environments.
An example of such a subclass is GregorianCalendar.
Calendar provides no public constructors.
Calendar defines several protected instance variables.
areFieldsSet is a boolean that indicates if the time components have been set.
fields is an array of ints that holds the components of the time.
isSet is a boolean array that indicates if a specific time component has been set.
time is a long that holds the current time for this object.
isTimeSet is a boolean that indicates if the current time has been set.

212. Calendar defines the following int constants, which are used when you get or set components of the calendar:

216. // Demonstrate Calendar
import java.util.Calendar;
class CalendarDemo {
public static void main(String args[])
String months[] = {"Jan", "Feb", "Mar", "Apr","May", "Jun", "Jul", "Aug",
"Sep", "Oct", "Nov", "Dec"};
// Create a calendar initialized with the
// current date and time in the default
// locale and timezone.
Calendar calendar = Calendar.getInstance();
// Display current time and date information.
System.out.print("Date: ");
System.out.print(months[calendar.get(Calendar.MONTH)]);
System.out.print(" " + calendar.get(Calendar.DATE) + " ");
System.out.println(calendar.get(Calendar.YEAR));
System.out.print("Time: ");
System.out.print(calendar.get(Calendar.HOUR) + ":");
System.out.print(calendar.get(Calendar.MINUTE) + ":");
System.out.println(calendar.get(Calendar.SECOND));
// Set the time and date information and display it.
calendar.set(Calendar.HOUR, 10);
calendar.set(Calendar.MINUTE, 29);
calendar.set(Calendar.SECOND, 22);
System.out.print("Updated time: "); }

217. GregorianCalendar
GregorianCalendar is a concrete implementation of a Calendar that implements the normal Gregorian calendar with which you are familiar.
The getInstance( ) method of Calendar returns a GregorianCalendar initialized with the current date and time in the default locale and time zone.
GregorianCalendar defines two fields: AD and BC.
These represent the two eras defined by the Gregorian calendar.
There are also several constructors for GregorianCalendar objects.
The default, GregorianCalendar( ), initializes the object with the current date and time in the default locale and time zone.
Three more constructors offer increasing levels of specificity:
GregorianCalendar(int year, int month, int dayOfMonth)
GregorianCalendar(int year, int month, int dayOfMonth, int hours, int minutes)
GregorianCalendar(int year, int month, int dayOfMonth, int hours, int minutes, int seconds)
All three versions set the day, month, and year. Here, year specifies the number of years
that have elapsed since The month is specified by month, with zero indicating January. The day of the month is specified by dayOfMonth. The first version sets the time to midnight. The second version also sets the hours and the minutes. The third version adds seconds.

218. boolean isLeapYear(int year)
You can also construct a GregorianCalendar object by specifying either the locale and/or time zone. The following constructors create objects initialized with the current date and time using the specified time zone and/or locale:
GregorianCalendar(Locale locale)
GregorianCalendar(TimeZone timeZone)
GregorianCalendar(TimeZone timeZone, Locale locale)
GregorianCalendar provides an implementation of all the abstract methods in Calendar. It also provides some additional methods. Perhaps the most interesting is isLeapYear( ), which tests if the year is a leap year. Its form is
boolean isLeapYear(int year)
This method returns true if year is a leap year and false otherwise.

219. import java.util.*;
class GregorianCalendarDemo {
public static void main(String args[])
String months[] = {"Jan", "Feb", "Mar", "Apr","May", "Jun", "Jul", "Aug","Sep", "Oct", "Nov", "Dec"};
int year;
// Create a Gregorian calendar initialized
// with the current date and time in the
// default locale and timezone.
GregorianCalendar gcalendar = new GregorianCalendar();
// Display current time and date information.
System.out.print("Date: ");
System.out.print(months[gcalendar.get(Calendar.MONTH)]);
System.out.print(" " + gcalendar.get(Calendar.DATE) + " ");
System.out.println(year = gcalendar.get(Calendar.YEAR));
System.out.print("Time: ");
System.out.print(gcalendar.get(Calendar.HOUR) + ":");
System.out.print(gcalendar.get(Calendar.MINUTE) + ":");
System.out.println(gcalendar.get(Calendar.SECOND));
// Test if the current year is a leap year
if(gcalendar.isLeapYear(year))
System.out.println("The current year is a leap year"); }
else {
System.out.println("The current year is not a leap year");

220. TimeZone
Another time-related class is TimeZone. The TimeZone class allows you to work with time zone offsets from Greenwich mean time (GMT), also referred to as Coordinated Universal Time (UTC). It also computes daylight saving time. TimeZone only supplies the default constructor.

222. import java.util.*;
public class TimeZones {
public static void main(String[] args)
Date date = new Date();
String TimeZoneIds[] = TimeZone.getAvailableIDs();
for(int i = 0; i < TimeZoneIds.length; i++)
TimeZone tz = TimeZone.getTimeZone(TimeZoneIds[i]);
String tzName = tz.getDisplayName(tz.inDaylightTime(date), TimeZone.LONG);
System.out.print(TimeZoneIds[i] + ": ");
// Get the number of hours and minutes from GMT
int rawOffset = tz.getRawOffset();
int hour = rawOffset / (60*60*1000);
int minute = Math.abs(rawOffset / (60*1000)) % 60;
System.out.println(tzName + " " + hour + ":" + minute); }

223. Locale
The Locale class is instantiated to produce objects that each describe a geographical or cultural region.
It is one of several classes that provide you with the ability to write programs that can execute in several different international environments.
For example, the formats used to display dates, times, and numbers are different in various regions.
Internationalization is a large topic that is beyond the scope of this book.
However, most programs will only need to deal with its basics, which include setting the current locale.
The Locale class defines the following constants that are useful for dealing with the most common locales:
CANADA GERMAN KOREAN
CANADA_FRENCH GERMANY PRC
CHINA ITALIAN SIMPLIFIED_CHINESE
CHINESE ITALY TAIWAN
ENGLISH JAPAN TRADITIONAL_CHINESE
FRANCE JAPANESE UK
FRENCH KOREA US

224. static void setDefault(Locale localeObj)
For example, the expression Locale.CANADA represents the Locale object for Canada. The constructors for Locale are
Locale(String language)
Locale(String language, String country)
Locale(String language, String country, String data)
These constructors build a Locale object to represent a specific language and in the case of the last two, country. These values must contain ISO-standard language and country codes. Auxiliary browser and vendor-specific information can be provided in data. The first constructor was added by Java 2, version 1.4.
Locale defines several methods. One of the most important is setDefault( ), shown here:
static void setDefault(Locale localeObj)
This sets the default locale to that specified by localeObj. Some other interesting methods are the following:
final String getDisplayCountry( )
final String getDisplayLanguage( )
final String getDisplayName( )

225. import java.text.*;
import java.util.Locale;
public class SettingLocale {
public static void main(String[] args)
// Getting default locale
Locale locale = Locale.getDefault();
System.out.println("Before setting, Locale is = " + locale);
// Setting default locale
locale = Locale.ITALY;
Locale.setDefault(locale);
System.out.println("After setting, Locale is = " + locale); }

226. Random
The Random class is a generator of pseudorandom numbers. These are called pseudorandom numbers because they are simply uniformly distributed sequences. Random defines the following constructors:
Random( )
Random(long seed)
The first version creates a number generator that uses the current time as the starting, or seed, value. The second form allows you to specify a seed value manually.

227. // Demonstrate random Gaussian values.
import java.util.Random;
class RandDemo {
public static void main(String args[])
Random r = new Random();
for(int i=0; i<100; i++)
System.out.println("The Next Gaussian Number is:" r.nextGaussian()); }

228. Currency
Java 2, version 1.4 adds the Currency class. This class encapsulates information about a currency. It defines no constructors.

229. // Demonstrate Currency.
import java.util.*;
class CurDemo {
public static void main(String args[])
Currency c;
c = Currency.getInstance(Locale.US);
System.out.println("Symbol: " + c.getSymbol());
System.out.println("Default fractional digits: " c.getDefaultFractionDigits()); }

230. JDBC – ODBC DRIVERS

231. JDBC DRIVERS Type of JDBC Drivers
The JDBC API defines the Java interfaces and classes that programmers use to connect to databases and send queries. A JDBC driver implements these interfaces and classes for a particular DBMS vendor.
A Java program that uses the JDBC API loads the specified driver for a particular DBMS before it actually connects to a database. The JDBC DriverManager class then sends all JDBC API calls to the loaded driver.
Type of JDBC Drivers
JDBC – ODBC Bridge
Native – API Partly Java Driver
JDBC – Net pure Java Driver
Native – Protocol Pure Java Driver

232. JDBC – ODBC bridge plus ODBC driver, also called Type 1.
Translates JDBC API calls into Microsoft Open Database Connectivity (ODBC) calls that are then passed to the ODBC driver. The ODBC binary code must be loaded on every client computer that uses this type of driver.
Native – API, partly Java driver, also called Type 2.
Converts JDBC API calls into DBMS-specific client API calls. Like the bridge driver, this type of driver requires that some binary code be loaded on each client computer.
JDBC – Net, pure Java driver, also called Type 3.
Sends JDBC API calls to a middle-tier net server that translates the calls into the DBMS-specific network protocol. The translated calls are then sent to a particular DBMS.
Native – protocol, pure Java driver, also called Type 4.
Converts JDBC API calls directly into the DBMS-specific network protocol without a middle tier. This allows the client applications to connect directly to the database server.

233. JDBC Implementation
JDBC is implemented as the java.sql.package. Some of the classes of this package are:
CLASSES
PACKAGES
Drivers
java.sql.Driver
java.sql.DriverManager
java.sql.DriverPropertyInfo
Connection
java.sql.Connection
Statements
java.sql.Statement
java.sql.PreparedStatement
java.sql.CallableStatement
ResultSet
java.sql.ResultSet
Exceptions
java.sql.SQLException
Date
java.sql.Date

234. Class.forName(“sun.jdbc.odbc.JdbcOdbcDriver”);
How to Java Application or Applets Connected to the Database
Loading the Driver
Making the Connection
Creating and Executing a JDBC statement
Retrieving Data From the Result Sets
Loading the Driver
If you are using the JDBC – ODBC Bridge driver, use the following statement to load it.
Class.forName(“sun.jdbc.odbc.JdbcOdbcDriver”);
2. Making the Connection
To get the driver connected to the database, which is done by creating a Connection object and initializing it with connection obtained from the DriverManager
Connection con = DriverManager.getConnection(url,
“LoginName”, “pwd”);

235. Statement stmt = con.createStatement();
3. Creating and executing a JDBC statement
a. A statement object is used to send the SQL statement to the database.
b. You create a statement object and then execute it, supplying the appropriate execute method with the SQL statement you want to send.
c. For a SELECT statement, the method used is executeQuery. For statements that create or modify tables, the method used is executeUpdate
Statement stmt = con.createStatement();
Example:
stmt.executeQuery (SELECT * FROM MARK WHERE SLNO = "+ t1.getText() +"“);
Stmt.executeUpdate(UPDATE MARK SET SLNO="+ s1 +",NAME='"+ s2 +"'
WHERE SLNO="+ s1 +“);

236. ResultSet rs = stmt.executeQuery (“select * from mark”);
4. Retrieving Data from the Result Sets
JDBC uses ResultSet object to return the output. So the previous executeQuery statement can be fully written as:
ResultSet rs = stmt.executeQuery (“select * from mark”);

237. IMPORTANT PROGRAMS

238. JAVA APPLICATION PROGRAMS
Simple Interest Calculation
Interest = P * N * R
P -> Principal Amount
N -> No. of Periods
R -> Rate of Interest
Compound Interest Calculation
Interest = P(1+(R/100))n
n -> No. of Periods
Celsius to Fahrenheit and Fahrenheit to Celsius

239. Write a simple menu driven calculator program using switch statement.
Write a program for Electricity Bill Preparation for the following condition:
1 – 50 Units paise
51 – 100 Units paise
101 – 200 Units - Rs. 1.50
201 – 600 Units - Rs. 2.20
Above 600 Units - Rs. 3.50
Write a program to Multiply for the two Matrices, Addition of the two Matrics and Subtraction of Two Matrics.
Write a program to find factorial of a given number
Write a program to check whether the given no is Palindrome or Not
Write a program to sort numbers in an array in ascending order and descending order

240. Applet Programs Write a program to given no. is prime or Not.
Write a program to generate Fibonacci Series Up to N numbers.
Applet Programs
Write a applet program to the creating Student Mark Statement.
Write a applet program to the creating Empolyee Salary Bill Preparation.
Write a applet program to the creating EB Bill Preparation.
Write a applet program to the Inventory Management System.
Write a applet program to the Hospital Management System.

241. Write a applet program to the creating User Authentication (username and password)
Write a applet program to the following Events
1. ActionEvent
2. AdjustmentEvent
3. FocusEvent
4. ItemEvent
5. MouseEvent (including MouseMotion)
6. KeyEvent
7. TextEvent
Write a applet program to the JDBC – ODBC drivers program for the above Applet program.

242. THE END