1. Chapter 5: Control Statements
Control Flow: A control flow Statement regulates the order in which statements get executed.
Flow-order in which the computer executes the lines of code in our program
Control flow blocks are basically blocks of code that control the way data flows, or else which statements are executed when. This can be useful if you only want certain areas of your code to be executed under a given condition.

2. The default flow of control in a program is TOP to BOTTOM, i. e
The default flow of control in a program is TOP to BOTTOM, i.e. all the statements of a program are executed one by one in the sequence from top to Bottom.
This execution order can be altered with the help of control instructions.
Java supports three types of control instructions -
1. Sequence Statement
2.Decision Making / Conditional / Selection Statements
3..Looping / Iterative Statements

3. Program Structure // comments about the class public class MyProgram {}
// comments about the method
public static void main (String[] args) { }
method header
method body

4. SEQUENCE
The sequence means the statements are being executed sequentially. This represents default flow of statement.
Statement 1
Statement 2
Statement 3

5. Condition ? Condition ? Condition ? Condition ? Condition ? Condition
SELECTION
The sequence Statements means the execution of statement(s) depending upon a given condition.
Condition ?
Condition ?
Condition ?
Condition ?
Condition ?
Condition ?
Condition?
Condition ?
Condition ?
Condition ?
Condition ?
Condition ?
Condition ?
Condition ?
Condition ?
false
false
false
false
false
false
false
true
true
true
Body of iF
Statement 1
Statement 1
Body of else
Statement 1
Statement 1
Statement 1
Statement 1
Statement 1
Statement 1
Statement 1
Statement 1
Statement 1
Statement 1
Statement 1
Statement 1
Statement 1
Statement 1
Statement 1
Statement 1
Statement 1
Statement 1
Statement 1
Statement 1
Statement 1
Statement 2
Statement 2
Statement 2
Statement 2
Statement 2
Statement 2
Statement 2
Statement 2
Statement 2
Statement 2
Statement 2
Statement 2
Statement 2
Statement 2
Statement 2
Statement 2

6. Conditional Statement - if Statement First Form of if Statement
if ( <conditional expression> ) {
execute statements -for-the-true-case; }
=>Second form
if ( < conditional expression > ) {
execute statement1 -for-the-true-case
else {
execute statement2 -for-the-false-case
Result of conditional expression : Logical Type(true or false)

7. The conditional expression is always enclosed in parenthesis.
There are certain points worth remembering about the if statement as outlined below:
The conditional expression is always enclosed in parenthesis.
The conditional expression may be a simple expression or a compound expression.
Each statement block may have a single or multiple statements to be executed.

8. In case there is a single statement to be executed then it is not mandatory to enclose it in curly braces ({}) but if there are multiple statements then they must be enclosed in curly braces ({})
The else clause is optional and needs to be included only when some action is to be taken if the test condition evaluates to false.

9. Example if ( j<5 ) { // This is recommended if ( j<5 )
System.out.println(“j is less than 5”): }
Else {
System.out.println(“j is no less than 5”): OR
if ( j<5 )
System.out.println(“j is less than 5”): //single statement
else

10. Syntax for the if Statement
if ( <boolean expression> )
<then block>
else
<else block>
Boolean Expression
Can be visualized as a flowchart
if ( testScore < )
JOptionPane.showMessageDialog(null, "You did not pass" );
else
JOptionPane.showMessageDialog(null, "You did pass " );
Then Block
Else Block
Indentation is important!

11. Nested if statement
if (<cond. expr.>)
// . . .
<statement>
if (<cond. expr.1>) <statement 1>
else if (<cond. expr.2>) < statement 2> …
else if (<cond. expr. n>) < statement n>
else < statement>

13. Conditional Operator(?)
if (x > 0) {
y = 1 }
else
y = -1;
is equivalent to
y = (x > 0) ? 1 : -1;

14. Syntax for the switch Statement
switch ( <arithmetic expression> ) {
<case label 1> : <case body 1> …
<case label n> : <case body n> }
Arithmetic Expression
switch ( gradeLevel ) {
case 1: System.out.print("Go to the Gymnasium");
break;
case 2: System.out.print("Go to the Science Auditorium");
case 3: System.out.print("Go to Harris Hall Rm A3");
case 4: System.out.print("Go to Bolt Hall Rm 101"); }
Case Label
Case Body
This is the general syntax rule for a switch statement. The case body may contain zero or more statements.

15. System.out.println(“go to 1”);
Example
switch(x) {
case 1:
System.out.println(“go to 1”);
break; // what happened if break is not here?
case 2:
case 3:
System.out.println(“go to 2 or 3”);
break;
default :
System.out.println(“not 1, 2 or 3”); }

16. =>The expression of switch must not be long, float, double, or Boolean, it must be either byte, short, char, or int. (assignment compatible with int)
=>The arguments to case labels must be constants, or at least a constant expression that can be fully evaluated at compile time.
=>Can not use a variable or expression involving variables.
=>Default clause can be placed any where in, the block.
=> The fall of control to the following cses of matching case is called FALL –THROUGH.

17. Switch
There are times in which you wish to check for a number of conditions, and to execute different code depending on the condition. One way to do this is with if/else logic, such as the example below:
int x = 1; int y = 2;
if (SOME_INT == x)
{ //DO SOMETHING }
else if (SOME_INT == y)
{ //DO SOMETHING ELSE }
else
{ //DEFAULT CONDITION }

18. This works, however another structure exists which allows us to do the same thing. Switch statements allow the programmer to execute certain blocks of code depending on exclusive conditions. The example below shows how a switch statement can be used:
int x = 1; int y = 2;
switch (SOME_INT) {
case x:
method1(SOME_INT);
break;
case y:
method2(SOME_INT);
default:
method3(); }

19. Switch takes a single parameter, which can be either an integer or a char. In this case the switch statement is evaluating SOME_INT, which is presumably an integer. When the switch statement is encountered SOME_INT is evaluated, and when it is equal to x or y, method1 and method2 are executed, respectively. The default case executes if SOME_INT does not equal x or y, in this case method3 is executed. You may have as many case statements as you wish within a switch statement.
Notice in the example above that "break" is listed after each case. This keyword ensures that execution of the switch statement stops immediately, rather than continuing to the next case. Were the break statement were not included "fall-through" would occur and the next case would be evaluated (and possibly executed if it meets the conditions).

20. Differences between the If-else and Switch ST:
Switch can only test for equality whereas if can evaluate a relational or logical expression that is multiple condition.
The switch statement select its branches by testing the value of same variable whereas the
if-else construction allow you use a series of expression that may involve unrelated variables and complex expressions.
The if-else is more versatile of the two statements.
The if-else statement can handle floating-point tests also apart from handling integer and character test whereas a switch cannot handle floating-point test. the case labels of switch must be an integer byte,short,int or a char.
The switch case label value must be a constant. so if two or more variables are to be compared ,use if-else.
The switch statement is more efficient choice in terms of code used in a situation that supports the nature of switch operation( testing a value against a se of constant).

21. Repetitions
for Loops
while Loops
do Loops
break and continue

22. Looping / Repetitive Statement
Some time some portion of the program (one or more statement) needs to be executed repeatedly for fixed no. of time or till a particular condition is being satisfied. This repetitive operation is done through a looping statement.
Definition
A loop is repetition of one or more instructions, which continues till certain condition is met.

23. Statement 1 Statement 2 Statement n ITERATION / LOOP
Looping structures are the statements that execute instructions repeatedly until a certain condition is fulfilled(true).
Condition ?
false
True
Statement 1
Statement 2
Statement n

24. In an Entry-Controlled loop/Top-Tested/Pre-Tested loop the test expression is evaluated before entering into a loop.
for Examples: For loop and While loop.
In an Exit-Controlled loop/Bottom-Tested/Post-Tested loop the test expression is evaluated before exiting from the loop.
for Examples: do-While loop.
Do not put a semicolon after the right parenthesis. If you do, the for loop would think that there no statements to execute. it would continue looping, doing nothing each time until the test expression becomes false.

25. for Loops int i; for (i = 0; i<100; i++)
for (initialization; Test-condition; update-statement) {
//loop body; }
Example:
int i;
for (i = 0; i<100; i++)
System.out.println("Welcome to Java! ” + i);

26. In for loop contains three parts separated by semicolons(;)
Initialization Before entering in a loop, its variables must be initialized. The initialization expression is executed only once in the beginning of the loop.
Test Expression It decides whether the loop-body will be executed or not. if the test expression evaluates to true the loop-body gets executed, otherwise the loop is terminated. Test expression gets checked every time before entering in the body of the loop.
Update Expression(s) The update expressions change the values of loop variables. The update expression is executed every time after executing the loop-body .
The body of the loop The statements that are executed repeatedly (as long as the test-expression is nonzero) from the body of the loop.

27. for Loop Flow Chart

28. for // print 1 2 3 4 5 6 7 8 9 10 public class ClassXI {
public static void main(String args[])
int n;
for(n=1; n<=10; n++)
System.out.println(“ ” + n);
}// end for loop
}// end main
} // end class

29. System.out.println(“ An infinite for Loop”); }
INFINITE LOOP: An infinite loop can be created by omitting the test expression as shown below:
for( int j=25; ; --j) {
System.out.println(“ An infinite for Loop”); }
2. for ( ; ; ) // infinite loop

30. 3.Empty Loop: If a loop does not contain any statement in its loop-body, it is said to be an empty loop. For(int j=20;j>=0;--j); 4. Declaration of variable inside the loops and if: A variable declared within an if or for/while/do-while statement cannot be accessed after the statement is over, because its scope becomes the body of the statement(if/for/while/ do-while). It cannot be accessed outside the statement body.

31. System.out.print(ans); // invalid
if( ch= =‘a’) {
int ans=1; }
else
int b=2;
System.out.print(ans);
// invalid
for( int ans=1; ans<100; ans+=20)
System.out.print(“ ” +ans);//valid
System.out.print(ans);//invalid
=>A variable scope is the part of program within which you can access the variable . A variable scope is the block of code( that is the part of code enclosed within{}) where the variable has been declared.

32. while Loops while (condition) { // loop-body; }
Note: A while loop is pre-test loop. It first tests a specified conditional expression and as long as the conditional expression is evaluated to non zero (true), action taken (i.e. statements or block after the loop is executed).

33. while Loop Flow Chart
START

34. while // Demonstrate the while loop. public class While {
public static void main(String args[]) {
int n = 1;
while(n<=1 0) {
System.out.println(“ " + n);
n++;
} //end while
} // end main
} // end class

35. do Loops do { // Loop body; } while (continue-condition);
The Do-while loop is an POST-TEST or bottom test loop.that is, it executes its body at least once without testing specified conditional expression and then makes test. the do-while loop terminates when the text expression is evaluated to be False(0).

36. do Loop Flow Chart

37. do-while // Demonstrate the do-while loop. public class DoWhile {
public static void main(String args[]) {
int n =1;
do {
System.out.println(" " + n);
n++;
} while(n <= 0);
} // main
} // class

38. Jump Java supports three jump statements:
break,
continue, and
return.
These statements transfer control to another part of your program.

39. break In Java, the break statement has three uses.
First, as you have seen, it terminates a statement sequence in a switch statement.
Second, it can be used to exit a loop.
Third, it can be used as a "civilized" form of goto.
java does not support goto statement

40. Labeled break statement
Alter flow of control
Causes immediate exit from control structure
Used in while, for, do…while or switch statements
Labeled break
Labeled block
Set of statements enclosed by { }
Preceded by a label
Labeled break statement
Exit from nested control structures
Proceeds to end of specified labeled block

41. break The general form of the labeled break statement is shown here:
break label;

42. The break Keyword

43. break // Using break to exit from for loop. class BreakLoop {
public static void main(String args[]) {
for(int i=0; i<100; i++) {
if(i = = 10)
break; // terminate loop if i is 10
System.out.println(“ i: " + i); }
System.out.println("Loop complete.");

44. break // Using break to exit from while loop. class BreakLoop2 {
public static void main(String args[]) {
int i = 0;
while(i < 100) {
if(i == 10) break; // terminate loop if i is 10
System.out.println("i: " + i);
i++; }
System.out.println("Loop complete.");

45. break // Using break to exit from do while loop. class BreakLoop2 {
public static void main(String args[]) {
int i = 0; do {
if(i == 10)
break; // terminate loop if i is 10
System.out.println("i: " + i);
i++;
} while(i < 100); }
System.out.println("Loop complete.");

46. Branch Statement - break Statement
To move control to the out of the block
From of break statement
break [label] ;
int i = 1;
while (true) {
if (i = = 3)
break;
System.out.println("This is a " + i + " iteration");
++i; }

47. continue
you might want to continue running the loop, but stop processing the remainder of the code in its body for particular iteration. This is, in effect, a goto just past the body of the loop, to the loop's end.
In while and do-while loops, a continue statement causes control to be transferred directly to the conditional expression that controls the loop.
In a for loop, control goes first to the iteration portion of the for statement and then to the conditional expression.

48. Labeled continue statement
As with the break statement, continue may specify a label to describe which enclosing loop to continue.
Skips remaining statements in loop body
Proceeds to next iteration
Used in while, for or do…while statements
Labeled continue statement
Skips remaining statements in nested-loop body
Proceeds to beginning of specified labeled block

49. The continue Keyword

50. // Demonstrate continue.
class Continue {
public static void main(String args[]) {
for(int i=0; i<10; i++) {
System.out.print(i + " ");
if (i%2 == 0)
continue;
System.out.println(""); }

51. // Using continue with a label.
class ContinueLabel {
public static void main(String args[]) {
outer: for (int i=0; i<10; i++) {
for(int j=0; j<10; j++) {
if(j > i) {
System.out.println();
continue outer; }
System.out.print(" " + (i * j));

52. Branch Statement – continue Statement
To move control to the start of next repeatation
From of continue statement
continue [Label] ;
When used in for statement
for (i=0; i<=5; ++i) {
if (i % 2 == 0)
continue;
System.out.println("This is a " + i + " iteration"); }

53. Branch Statement – continue Statement
When used in while statement
i = 0;
while (i <= 5) {
++i;
if (i % 2) == 0)
continue;
System.out.println("This is a odd iteration - " + i); }

54. Branch Statement – continue Statement
Label continue statement
[LabeledContinue.java]
labelName:
Rep. St. 1 {
Rep. St. 2 {
// ...
continue;
continue labelName; }

55. return
The return statement is used to explicitly return from a method. That is, it causes program control to transfer back to the caller of the method.
The following example illustrates this point. Here, return causes execution to return to the Java run-time system, since it is the run-time system that calls main( ).

56. Branch Statement – return Statement
To terminate the execution of method, then pass the method of caller that control
Forms of return statement
return;
return <expr.>;

57. return // Demonstrate return. class Return {
public static void main(String args[]) {
boolean t = true;
System.out.println("Before the return.");
if(t) return; // return to caller
System.out.println("This won't execute."); }

58. END

59. Objects and Classes
Object = active program unit containing both data and procedures
Class = a template for all objects of the same type
An Object is often called an instance of the class.

60. Components of an object
Instance variable = variable within an object
Method = function or procedure within an object
Can manipulate the object’s instance variables
Constructor = special method to initialize a new object instance

61. Encapsulation
Encapsulation = a way of restricting access to the internal components of an object
Private
Public

62. Additional object-oriented concepts
Inheritance: allows new classes to be defined in terms of previously defined classes
Polymorphism: allows method calls to be interpreted by the object that receives the call

63. Figure 6.22 The structure of a class describing a laser weapon in a computer game

64. Figure 6.23 A class with a constructor

65. Figure 6.24 Our LaserClass definition using encapsulation as it would appear in a Java or C# program

66. Programming concurrent activities
Parallel or concurrent processing = simultaneous execution of multiple processes
True concurrent processing requires multiple CPUs
Can be simulated using time-sharing with a single CPU

67. Interaction between processes
Mutual exclusion = a method for ensuring that data can be accessed by only one process at a time
Monitor = a data item augmented with the ability to control access to itself

68. Figure 6.25 Spawning processes

69. Comparing Objects
With primitive data types, we have only one way to compare them, but with objects (reference data type), we have two ways to compare them
We can test whether two variables point to the same object (use ==), or We can test whether two distinct objects have the same contents.
String str1 = new String("Java");
String str2 = new String("Java");
if (str1 == str2) {
System.out.println("They are equal"); }
else {
System.out.println("They are not equal");
Solution : They are not equal
Discussion of some string methods

70. Explanation of the above Program:
When we use the equality operator (==), we can comparing the contents of the variables str1 and str2. So str1 == str2 being true means the contents are the same, which in turn, means they are pointing to the same object because the content of a reference data type is an address. Therefore, if there are two distinct objects, even the values hold by these objects are the same, the equality testing by the equality operator will always result in false.

72. PROGRAM
import javax.swing.*; // To support simple input
public class Control { // Quadratic formula
public static void main(String[] args) {
final double TOL= 1E-15; // Constant(use ‘final’)
String input;
input= JOptionPane.showInputDialog("Enter a");
double a= Double.parseDouble(input);
input= JOptionPane.showInputDialog("Enter b");
double b= Double.parseDouble(input);
input= JOptionPane.showInputDialog("Enter c");
double c= Double.parseDouble(input);

73. double discriminant= b*b - 4.0*a*c;
if ( discriminant < 0)
System.out.println("Sorry, no real root");
else if (Math.abs(discriminant) <= TOL) {
double root= -0.5 * b / a;
System.out.println("Root is " + root); }
else { // Redefine ‘root’; blocks have own scopes
double root=(-b + Math.sqrt(discriminant))/
(2.0*a);
double root2=(-b- Math.sqrt(discriminant))/
System.out.println("Roots" + root + “," +
root2); }
System.exit(0); } }

74. Arithmetic Operators Intro to OOP with Java,=> C. Thomas Wu
The precedence table shows the order of operator evaluation. Instead of memorizing this table, it is more convenient and the code more readable if you use the parentheses judiciously.

75. Operator Precedence Rules

76. Repetition Statements
Selection Statements
Using if and if...else
Nested if Statements
Using switch Statements
Conditional Operator
Repetition Statements
Looping: while, do, and for
Nested loops
Using break and continue
Note: Java does NOT support goto

77. Java Statement Assign Statement. : var = exp Statement
Compound Statement : { }
Condition Statement. : if St., switch St.
Control Loop Statement. : for St., while St., do-while St.
Branch Statement. : break St., continue St., return St.
Exception Handling St.: try-catch-finally
Synchronization St : synchronized
Standard I/O : System.in.read(), System.out.println()
Assignment Statement: Assign the value to variable
Form : <variable> = <expression>
remainder = dividend % divisor;
i = j = k = 0; x *= y;
Statement