Java Flow Controls.pptxJava Flow Controls.pptxJava Flow Controls.pptx

Control Statements © 2017 wipro.co confidentia 4  Control statements are statements which alter the normal execution flow of a program  There are three types of Control Statements in java Selection statement Iteration Statement Jumping Statement if if – else switch while for do – while break continu e return

If - Example /* This is an example of a if statement */ public class Test { public static void main(String args[]) { int x = 5; if( x < 20 ) { System.out.print("This is if statement"); } } } Output: This is if statement © 2017 wipro.co confidentia 6

If..else statement The if….else statement is an extension of simple if statement Syntax: if(boolean expression) { True-block statements; } else { False-block statements; } Next statement; Boolean expression? True-block False-block Next Statement Entry © 2017 wipro.co confidentia 7 True False

If – else Example © 2017 wipro.co confidentia 8 /* program to check given age input is eligible to vote or not using if- else*/ public class Check { public static void main(String[ ] args) { int age; age = Integer.parseInt(args[0]); if(age>18) { System.out.println("Eligible to vote"); } else { System.out.println("Not eligible to vote"); } }

else - if Example © 2017 wipro.co confidentia 10 /* program to print seasons for a month input using if & else if */ public class ElseIfDemo { public static void main(String[] args) { int month = Integer.parseInt(args[0]); if(month == 12 || month == 1 || month == 2) System.out.println("Winter"); else if(month == 3 || month == 4 || month == 5) System.out.println("Spring"); else if(month == 6 || month == 7 || month == 8) System.out.println("Summer"); else if(month == 9 || month == 10 || month == 11) System.out.println("Autumn"); else System.out.println("invalid month"); } } If args[0] is 6 then the Output is : Summer

Switch Case © 2017 wipro.co confidentia 11  The switch-case conditional construct is a more structured way of testing for multiple conditions rather than resorting to a multiple if statement Syntax: switch (expression) { case value-1 : case-1 block break; case value-2 : case-2 block b reak; default : default block break; } statement-x;

Switch Case - Example /* This is an example of a switch case statement*/ public class SwitchDemo { public static void main(String[] args) { int weekday = Integer.parseInt(args[0]); switch(weekday) { case 1: case 2: case 3: case 4: case 5: case 6: case 7: default: System.out.println(“Sunday"); break; System.out.println(“Monday"); break; System.out.println(“Tuesday"); break; System.out.println(“Wednesday"); break; System.out.println(“Thursday"); break; System.out.println(“Friday"); break; System.out.println(“Saturday"); break; System.out.println(“Invalid day"); } } } If args[0] is 6 then the Output is : Friday © 2017 wipro.co confidentia 12

while loop – Example /* This is an example for a while loop */ public class Sample{ public static void main(String[] args) { int i = 0; while (i < 5) { System.out.println("i: "+i); i = i + 1; } } } Output: i: 0 i: 1 i: 2 i: 3 i: 4 © 2017 wipro.co confidentia 14

do…while loop – Example /* This is an example of a do-while loop */ public class Sample { public static void main(String[] args) { int i =5; do { Syste m.out .prin tln(" i: "+i); i = i } } Output: i: 5 © 2017 wipro.co confidentia 16

For loop - Example /* This is an example of a for loop */ public class Sample { public static void main(String[] args) { for (int i=1; i<=5; i++ ) { System.out.println("i: "+i); } } } Output: i: 1 i: 2 i: 3 i: 4 i: 5 © 2017 wipro.co confidentia 18

Enhanced for loop - Example /* This is an example of a enhanced for loop */ public class Sample { public static void main(String[] args) { int [] numbers = {10, 20, 30, 40, 50}; for(int i : numbers ) { System.out.println( "i: "+i ); } } } Output : i:10 i:2 0 i: 30 i:40 i:50 © 2017 wipro.co confidentia 20

break statement © 2017 wipro.co confidentia 21  While the execution of program, the break statement will terminate the iteration or switch case block  When a break statement is encountered in a loop, the loop is exited and the program continues with the statements immediately following the loop  When the loops are nested, the break will only terminate the corresponding loop body

break - Example /* This is an example of a break statement */ public class Sample{ public static void main(String[] args) { for (int i=1; i<=5; i++ ) { if(i==2) break; System.out.println("i: "+i); } } } Output : i: 1 © 2017 wipro.co confidentia 22

continue statement © 2017 wipro.co confidentia 23  The continue statement skips the current iteration of a loop  In while and do loops, continue causes the control to go directly to the test-condition and then continue the iteration process  In case of for loop, the increment section of the loop is executed before the test- condition is evaluated

© 2017 wipro.co confidentia 24 Continue - Example /* This is an example of a continue loop */ public class Sample { public static void main(String[] args) { int [] numbers = {1, 2, 3, 4, 5}; for(int i : numbers ) { if( i == 3 ) { continue; } System.out.println( "i : "+i ); } } } Output : i: 1 i:2 i:4 i:5

© 2017 wipro.co confidentia 25 if statement  Always use {} for if statements  Avoid the following error prone if (condition) statement; switch-case statement Number per Line //ERROR  One declaration per line is recommended int height; int width; is preferred over int height,width; Do not put different types on the same line Good Programming Practices

What will be the result, if we try to compile and execute the following code ? class Sample{ public static void main(String[]args) { boolean b = true; if(b){ System.out.println(" if block "); } else { System.out.println(“ else block "); } } } © 2017 wipro.co confidentia 26 Quiz

What will be the result, if we try to compile and execute the following code snippets 1. class Sample { public static void main(String[] args) { while(false) System.out.println("while loop"); } } 2. class Sample { public static void main(String[] args) { for( ; ; ) System.out.println("For loop"); } } © 2017 wipro.co confidentia 27 Quiz (Contd.).

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