1. Java Basics
Introduction to Java

2. Topics To Be Covered Objectives Introduction Features of Java
Java Architecture
Java Program Structure
Data Types in Java
Operations in Java
Console Input and Output
Control Structures
Summary
Quiz

3. Objectives At the end of this course, you will be able to:
Understand the Java Platform Architecture
Features of Java
Write programs using variables, expressions, console input/output
Data types and Operations in Java
Write programs using Control Structures

4. Introduction A high-level programming language
Operating System Independent
Runs on Java Virtual Machine (JVM)
A secure operating environment that runs as a layer on top of the OS
A sandbox which protects the OS from malicious code
True Object-Oriented Programming language
In Java, everything is a class
Unlike C++, OOP support is a fundamental component in Java

5. Features of Java

6. Features of Java Simple
Compares to earlier OO languages like C++, it is simple
Robust
Puts a lot of emphasis on early checking for possible problems, later dynamic (runtime) checking, and eliminating situations that are error-prone
Secure
Absence of pointers
Support for Multithreading at the language level
Designed to handle Distributed applications
Architecture Neutral/Portable:
Java code compiled on Windows can be run on Unix without recompilation

7. Features of Java Platform Independence
A platform is the hardware & software environment in which a program runs
Once compiled, java code runs on any platform without recompiling or any kind of modification “Write Once Run Anywhere”
This is made possible by Java Virtual Machine (JVM)

8. Java Overview
JAVA is platform independent language which means that the program made in java run on any operating system either it is window, IOS or Linux.
JAVA syntax is similar to C++.
A significant feature in java is multithreading. Several programs run at the same time in JAVA environment.

9. Java Overview The reason behind JAVA independency is :
It only depend on Java virtual Machine(JVM)
Code is compiled in bytecode, which is interpreted by JVM.

10. Java Architecture

11. Java Architecture Class Loader Source File (HelloWorld.java)
Compiler (javac)
Class Loader
Byte Code Verifier
Interpreter
Runtime
JIT Code Generator
Machine Code or Byte code (HelloWorld.class)
Operating System
Hardware

12. Java Architecture JDK Directory Structure
After installing the Java software version 1.5, the JDK directory will have the structure as shown
JDK Installation Directory
lib
bin …
The bin directory contains both, the computer and the interpreter

13. Write a Program Compiling Running
Java Architecture
Java Development Process
Write a Program Compiling Running
Compiler
Interpreter
Java Files
Public Class System
.class File

14. Java Architecture Java Virtual Machine (JVM)
We can write a Java program using any text editor or an IDE like Eclipse
(Version 3.2 onwards preferred).
The source code of Java is stored in a text file with the extension .java
The Java compiler complies a .java file into byte code
The byte code will be in a file with extension .class
The generated .class file is the machine code of this processor
Byte code is a binary language
The byte code is interpreted by the JVM
JVM makes Java platform independent
The JVM interprets the .class file to the machine language of the underlying platform
The underlying platform processes the commands given by the JVM

15. Java Architecture Environment Variables in JVM
JAVA_HOME: Java Installation Directory
Used to derive all other environment variables used by JVM
In Windows
set JAVA_HOME=C:\jdkxxxx
In Unix
export JAVA_HOME=/var/usr/java
CLASSPATH
Used to locate class files
In Windows
set CLASSPATH=%CLASSPATH%;%JAVA_HOME%\lib\tools.jar
In Unix
set CLASSPATH=$CLASSPATH:$JAVA_HOME%/lib/tools.jar
PATH
Used by OS to locate executable files
In Windows
set PATH=%PATH%;%JAVA_HOME%\bin
In Unix
set PATH=$PATH:$JAVA_HOME/bin

16. Java Program Structure

17. Java Program Structure
Source File Layout – Hello World
Type the source code using Eclipse (Version 3.2 onwards) or any text editor
public class HelloWorldApp {
public static void main(String[ ] args){
System.out.println("Hello World!"); }
Save this file as HelloWorldApp.java

18. Java Program Structure
To Compile
Open the command prompt
Set the environment variables
Go to the directory in which the program is saved
Type – javac HelloWorldApp.java
If it says, “bad command or file name” then check the path setting
If returns to prompt without giving ant message, it means that compilation is successful

19. Java Program Structure
To Execute
Type the command - java HelloWorldApp
The result will be

20. Java Program Structure
Compilation & Execution
Java Program (.java)
Java Complier (.javac)
Byte Code (.class file)
Interpreter (java)
Win 32
Linux
Mac

21. Java Program Structure
Java Keywords
abstract
continue if
int
switch
boolean
float
import
return
synchronized
break
default
false
package
static
byte do
interface
private
try
case
double
long
protected
throws
catch
else
goto*
native
this
char
extends
new
public
transient
class
final
implements
throw
void
true
finally
instanceof
short
volatile
const*
for
null
super
while

22. Java Program Structure
Java Identifiers
Declared entities such as variables, methods, classes & interfaces are Java Identifiers
Must begin with a letter, underscore (_) or dollar sign ($)
May contain letters, digits, underscore (_) & dollar sign ($)

23. How Java program Works
In the Java programming language, all source code is first written in plain text files ending with the .java extension. 
Those source files are then compiled into .class files by the javac compiler. 
The java launcher tool then runs your application with an instance of the Java Virtual Machine.

24. How Java program Works Compiler Java VMr 01001… MyProgram.java
MyProgram.class
MyProgram

25. Java Environment Setup
We now explain the commonly used steps in creating and executing a JAVA application using Java Development environment. There are five phases of creating and executing JAVA program:
Edit
Compile
Load
Verify
Execute

26. Java Environment Setup
Editor
Compiler
Class Loader
Bytecode Verifier
Java Virtual Machine (JVM)
Phrase 1: Edit
Phrase 2: Compile
Phrase 3: Load
Phrase 4: Verify
Phrase 5: Execute
Disk
Primary Memory
Program is created in an editor and stored on disk in a file ending with .java
Compiler create bytecodes and stores them on disk in a file ending with .class
Class loader reads .class files containing bytecodes from disk and puts those bytecodes in memory.
Bytecode verifier confirms that all bytecodes are valid and do not violate java’s security restrictions
To execute the program, the JVM reads bytecodes and translates them into a language that the computes can understand. As the program executes, it may store data values in primary memory.

27. Java Basic Syntax
A typical JAVA program has objects, classes, methods and instance.
Case Sensitivity: JAVA is case sensitive language. Word and word would have different meaning in JAVA.
Class-naming conventions: You can name classes pretty much however you want, but the convention is to use camel case. Start with an uppercase letter, capitalize the first letter of each concatenated word, and make all the other letters lowercase.
Example HelloClass

28. Sample Program #1 Java Sample Programs public class FirstJavaProgram {
public static void main(String[] args){
System.out.println("This is my first program in java");
} //End of main
}//End of FirstJavaProgram Class

29. Sample Program # 2 Java Sample Programs class Example{
public Static void main(String args[]){
// This is simple JAVA program
System.out.print(“ This is simple JAVA program ”); }

30. Java Basic Syntax
Method Naming Conventions: All method name start with lowercase.
If method name is made by more then one words then each word has first capital latter.
Program Name: Program file name should match with class name with extension of ’ .java ’ . Example your class name is HelloWorld then file name should be HelloWorld.java .
public static void main(String args[]) : Java program processing starts from the main() method which is a mandatory part of every Java program.

31. Data Types in Java

32. Data Types in Java Java is a strongly typed language Data types may be
Unlike C, Type checking is strictly enforced at run time
Impossible to typecast incompatible types
Data types may be
Primitive data types
Reference data types

33. Data Types in Java Primitive Data Types in Java
Integer Data Types
byte
(1 byte)
short
(2 bytes)
int
(4 bytes)
long
(8 bytes)
All numeric data types are signed
The size of data types remain same on all platforms
Char data type is 2 bytes as it uses the UNICODE character set. And so, Java supports internationalization
Floating Data Types
float
(4 bytes)
double
(8 bytes)
Character Data Types
char
(2 byte)
Logical Data types
boolean
(1 bit) (true/false)

34. Data Types in Java Variables
A named storage in the computer’s memory that stores a value of a particular type for use by program
Example of variable declaration:
The data type can either be:
built-in primitive types (e. g. int, double, char)
Reference data types (e.g. String, BufferedReader)
Naming Convention:
Variable Name: First word lowercase & rest with their initials capitalized (Camel Casing)
e.g. thisIsALongVariableName
DataType
VariableName
int
myAge, cellPhone ;
double
salary ;
char
tempChar ;

35. Data Types in Java Variables (Contd…)
Using primitive data types is similar to other languages
Variables can be declared anywhere in the program
In Java, if a local variable is used without initializing it, the compiler will show an error
int count ;
int max=100;
for (int count=0; count <max; count++) {
int z = count * 10; }
BEST PRACTICE:
Declare a variable in program only when required
Do not declare variables upfront like in C

36. Data Types in Java Comments in Java
A single line comment in Java starts with //
A multi line comment starts with /* & ends with */
// This is a single line comment in Java
/* This is a multi line
comment
in Java */

37. Data Types in Java Reference Data Types
Hold the reference of dynamically created objects which are in the heap
Can hold three kinds of values:
Class type: Points to an object / class instance
Interface type: Points to an object which is implementing the corresponding interface
Array type: Points to an array instance or “null”
Difference between Primitive & Reference data types:
Primitive data types hold values themselves
Reference data types hold reference to objects, i.e. they are not objects, but reference to objects
Objects & Arrays are accessed using reference variables in Java
A reference variable Is similar to a pointer (stores memory address of an object)
Java does not support the explicit use of addresses like other languages

38. Data Types in Java Reference Data Types (Contd…)
Java does not allow pointer manipulation or pointer arithmetic
Memory Representation:
primitive
reference
A reference type cannot be cast to a primitive type
A reference type can be assigned ‘null- to show that it is not referring to any
int primitive = 5;
String reference = “Hello” ; 5
Hello

39. Data Types in Java Typecasting Primitive Data Types
Automatic type changing is known as Implicit Conversion
- A variable of smaller capacity can be assigned to another variable of bigger capacity
Whenever a larger type is converted to a smaller type, we have to explicitly specify the type cast operator
This prevents any accidental loss of data
int i = 10;
double d;
d = i;
double d = 10;
d = i;
i = (int) d;
Type cast operator ()

40. Operations in Java

41. Operations in Java Used to manipulate primitive data types
Classified as unary, binary or ternary
Following are different operators in Java:
Assignment
Arithmetic
Relational
Logical
Bitwise
Compound assignment
Conditional
Java Operations
Assigment Operators =
Arithmetic Operations
- + * / %
Relational Operators
> < >= <= == !=
Logical Operators
&& || & | ! ^
Bit wise Operator
& | ^ >> >>>
Compound Assignment Operators
+= -= *= /= %= <<= >>= >>>=
Conditional Operator ?:

42. Operations in Java Precedence & Associativity of Java Operators
Decides the order of evaluation of operators

43. Console Input and Output

44. Console Input and Output
Accepting Data from Keyboard
import java.util.Scanner;
public class Datalnput {
public static void main(String args[ ]) {
Scanner input = new Scanner(System.in); System.out.println("Enter First Number-);
int a = input.nextlnt();
System.out.println("Enter Second Number");
int b = input.nextlnt();
int c = a + b;
System.out.prlntln(“Addition is..." + c); }
Like nextInt ( ) method,which scans the integer value, the Scanner class provides methods for other data types as well.

45. Control Structures

46. Control Structures Work the same as in C / C++
if/else, for, while, do/while, switch
i = 0;
while(i < 10) {
a += 1;
i++; }
do {
a += i;
} while(i < 10);
if(a > 3) {
a = 3;
else {
a = 0;
for(i = 0; i < 10; i++) {
switch(i) {
case 1:
string = “foo”;
case 2:
string = “bar”;
default:
string = “”;

47. Control Structures (Contd…)
Java supports continue & break keywords also
Again, works very similar to C / C++
Switch statements require the condition variable to be of char, byte, short or int type
for(i = 0; i < 10: i++) {
if(i == 5)
continue;
a += i; }
for(i = 0; i < 10: i++) {
a += i;
if(a > 100)
break; }

48. Summary

49. Summary In this session, we have covered: Java Architecture
Features of Java
Data types and Operators in Java
Control Structures

50. Assessment – Java Basics: Part1
The quiz contains 10 questions.
You will have one attempt to answer each question.
You can exit the quiz at any time.
If you exit the quiz without completing all 10 questions, on return you will have to start the quiz from the beginning.
Scoring 80% or higher means you have understood the topic well.
Start

51. Java Is Strongly Typed Language
True
False

52. Which of the following is not a feature of Java?
Multithreaded
Object Oriented
Platform Dependent

53. Conditional Operator (?:)
Which of the following operator in Java has associativity as Right to Left?
Conditional AND (&& )
Conditional Operator (?:)
Conditional OR ( II )

54. Find the odd one from below
while
do while
Untill while

55. Because of which Java is Platform Independent?
KVM
JVM
HVM

56. Which of the following is not accepted by Reference Variable?
Integer variable
Array
Object

57. Which of the following loads a .class file in memory?
Byte code verifier
Class Loader
JIT Code generator

58. Which of the following is not a valid identifier?
basicSal
12Number
empHra

59. Suppose x is a local variable in main method
Suppose x is a local variable in main method. If we print its value without initializing it then what will happen?
Will print 0
Will print 1
Compile time error

60. Why Java is a Secure programming language?
Absence of Pointers
Absence of Multithreading
Absence of Robustness

61. The Results