Control Statements in Java

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

1. Presented By Niloy Saha Control Statements in Java Department of Computer Science & Engineering

2. Control Statements Selection Iteration Jump Outlines 2

3. Selection Selection Statements Switch Statement Selection Statements are also called Decision Making Statements. Selection Statements 3

4. i f Statements Simple if i f else if- else- if Ladder Nested if i f Statements 4

5. Simple if Syntax : if (condition) { statement1; } Purpose: The statements will be evaluated if the value of the condition is true. 5

6. Simple if Start End Condition Statements False True Flow Chart: 6

7. Example 7

8. i f else Syntax : if (condition) { statement1; } else { statement2; } Purpose: The statement 1 is evaluated if the value of the condition is true otherwise statement 2 is true. 8

9. i f else False True Flow Chart : Start End Condition Statement 1 Statement 2 9

10. Example 10

11. If-else-if Ladder Syntax : if(condition)   statements; else if(condition)   statements; else if(condition)   statements; ... ... else   statements; 11

12. Examples import java.util.Scanner ; class Day { public static void main(String args []) { Scanner s = new Scanner(System.in); System.out.println (" Enet day between 0 to 6 Day = "); int day = s.nextInt (); if (day == 0) { System.out.println ("\n Sunday"); } else if (day == 1) { System.out.println ("\n Monday"); } else if (day == 2) { System.out.println ("\n Tuesday"); } else if (day == 3) { System.out.println ("\n Wednesday"); } else if (day == 4) { System.out.println ("\n Thursday"); } else if (day == 5) { System.out.println ("\n Friday"); } else { System.out.println ("\n Saturday"); } } } 12

13. Nested if A nested if is an if statement that is the target of another if or else. Nested ifs are very common in programming.  Syntax :   if(condition) {      if(condition)          statements....      else          statements.... } else {       if(condition)          statements....      else          statements.... }   13

14. Example 14

15. s witch Syntax : switch (expression) { case value 1 : statement 1 ; break; case value 2 : statement 2 ; break; ... ... case value N : statement N ; break; default : statements ; break; } Purpose: The statements N will be evaluated if the value of the logical expression is true . 15

16. switch Flow Chart: Case A Case B … default False False False Case A Statements break; Case B Statements break; Case C Statements break; Default Statements Start Variable or Expression True True True End 16

17. Example 17

18. Iteration Statements Iterations/ Loops while do while for Each loop has four types of statements : Initialization Condition checking Execution Increment / Decrement 18

19. while Syntax: initialization while(final value) { statements; increment/decrement; } Purpose: To evaluate the statements from initial value to final value with given increment/decrement. m=1 while(m<=20) { System.out.println(m); m=m+1; } 19

20. Example class while1 { public static void main(String args []) { int i =1; while( i <=10) { System.out.println("\n" + i ); i ++; } } } Output : 1 2 3 4 5 6 7 8 9 10 print values from 1 to 10 20

21. do while Syntax : initialization do { statements; increment/decrement; } while(final value); Purpose: To evaluate the statements from initial value to final value with given increment/decrement. m=1 do { System.out.println(m); m=m+1; } while(m==20); 21

22. Example class dowhile1 { public static void main(String args []) { int i = 1; int sum = 0; do { sum = sum + i ; i ++; }while ( i <=10); System.out.println("\n\n\ tThe sum of 1 to 10 is .. " + sum); } } Output : The sum of 1 to 10 is .. 55 22

23. for Syntax: for( initialization;final value;increment /decrement) { statements; } Purpose: To evaluate the statements from initial value to final value with given increment/decrement. for(m=1;m<=20;m=m+1) { System.out.println(m); } 23

24. Example class for1 { public static void main(String args []) { int i ; for ( i =0;i<5;i++) { System.out.println("\ nExample of for loop "); } } Output : Example of for loop Example of for loop Example of for loop Example of for loop Example of for loop 24

25. Jump Statements Jump break continue return 25

26. The break statement This statement is used to jump out of a loop. Break statement was previously used in switch – case statements. On encountering a break statement within a loop, the execution continues with the next statement outside the loop. The remaining statements which are after the break and within the loop are skipped. Break statement can also be used with the label of a statement. A statement can be labeled as follows. statementName : SomeJavaStatement When we use break statement along with label as, break statementName ; 26

27. Example class break1 { public static void main(String args []) { int i = 1; while ( i <=10) { System.out.println("\n" + i ); i ++; if ( i ==5) { break; } } } } Output : 1 2 3 4 27

28. c ontinue Statement This statement is used only within looping statements. When the continue statement is encountered, the next iteration starts. The remaining statements in the loop are skipped. The execution starts from the top of loop again. 28

29. Example class continue1 { public static void main(String args []) { for ( int i =1; i <1=0; i ++) { if (i%2 == 0) continue; System.out.println("\n" + i ); } } } Output : 1 3 5 7 9 29

30. The return Statement The last control statement is 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. T he return statement immediately terminates the method in which it is executed. 30

31. Example class Return1 { 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."); } } Output : Before the return. 31

32. Thank You