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# Control structures

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### Control structures

1. 1. Control structures University of Human Development
2. 2. Contents Comparison operators Control structures  if Statements  For Statement  switch Statement  while & do loop
3. 3. Comparison Operators == Tests whether two values are equal != Tests whether two values are not equal < Tests if left side value is less than to the right side value > Tests if left side value is greater than to the right side value <= Tests if left side value is less than or equal to the right side value >= Tests if left side value is greater than or equal to the right side value Operators
4. 4. if Statements Syntax : (1) he syntax of an if statement is if (conditional clause) { Statement(s) block }  There are three basic forms for an if statement:
5. 5. public class IT { public static void main(String args[]) { int x = 10; if ( x < 20 ) { System.out.print("This is if statement"); } } } Example
6. 6. Result
7. 7. Use when you want to do one thing or another thing Syntax: (2) if (conditional clause) { Statement(s) block } else { Statement(s) block } if. Else S…
8. 8. public class IT { public static void main(String args[]) { int x = 30; if( x < 20 ) { System.out.print("This is if statement"); } else{ System.out.print("This is else statement"); } } } Example
9. 9. Result
10. 10. if else if statement Syntax if (conditional clause) (3) { Statement(s) block } else if (conditional clause) { Statement(s) block } Use when there are three or more possibilities if statement
11. 11. User input Example
12. 12. Result User is…
13. 13. The for Loop : A for loop is a repetition control structure that allows you to efficiently write a loop that needs to execute a specific number of times. A for loop is useful when you know how many times a task is to be repeated.
14. 14. Syntax : The syntax of a for loop is: for (initialization; Boolean_expression; update) { //Statements } The for Loop
15. 15. Here is the flow of control in a for loop: The initialization step is executed first, and only once. This step allows you to declare and initialize any loop control variables. You are not required to put a statement here, as long as a semicolon appears. Next, the Boolean expression is evaluated The for Loop
16. 16. If it is true, the body of the loop is executed. If it is false, the body of the loop does not execute and flow of control jumps to the next statement past the for loop. After the body of the for loop executes, the flow of control jumps back up to the update statement The for Loop
17. 17. This statement allows you to update any loop control variables. This statement can be left blank, as long as a semicolon appears after the Boolean expression. The Boolean expression is now evaluated again. If it is true, the loop executes and the process repeats itself (body of loop, then update step, then Boolean expression). After the Boolean expression is false, the for loop terminates. The for Loop
18. 18. Example public class IT { public static void main( String args[]) { For ( int x = 10; x < 20; x = x+1) { System.out.print("value of x : " + x ); System.out.print("n"); } } }
19. 19. This would produce the following result : Result
20. 20. Switch Statement A switch statement allows a variable to be tested for equality against a list of values. Each value is called a case, and the variable being switched on is checked for each case.
21. 21. Syntax : The syntax of enhanced for loop is: Switch (expression) { case value : //Statements break; //optional case value : //Statements break; //optional //You can have any number of case statements. default : //Optional //Statements } Switch Statement
22. 22.  The following rules apply to a switch statement:  The variable used in a switch statement can only be a byte, short, int, or char.  You can have any number of case statements within a switch. Each case is followed by the value to be compared to and a colon.  The value for a case must be the same data type as the variable in the switch and it must be a constant or a literal. Switch Statement
23. 23.  When the variable being switched on is equal to a case, the statements following that case will execute until a break statement is reached.  When a break statement is reached, the switch terminates, and the flow of control jumps to the next line following the switch statement.  Not every case needs to contain a break. If no break appears, the flow of control will fall through to subsequent cases until a break is reached.  A switch statement can have an optional default case, which must appear at the end of the switch. The default case can be used for performing a task when none of the cases is true. No break is needed in the default case. Switch Statement
24. 24. Example:
25. 25. Result Compile and run above program using various command line arguments. This would produce the following result:
26. 26. While loop :
27. 27. While Loop Syntax
28. 28. Do - While Loop
29. 29. While Loop Syntax While Loop
31. 31. End
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