Java - case Keyword

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case Keyword

Java case keyword is a conditional label used with the switch statement which 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.

Syntax

The syntax of the case keyword with switch statement:

 switch(expression) { case value : // Statements break; // optional case value : // Statements break; // optional // You can have any number of case statements. default : // Optional // Statements } 

Rules

The following rules apply to a case keyword with switch statement −

• The variable used in a switch statement can only be integers, convertable integers (byte, short, char), strings and enums.

• 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.

• 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.

Flow Diagram

Examples of case Keyword

Example 1

In this example, we're showing use of switch statement where cases are based on a char. We've created a variable grade. Based on value of grade, each case is checked. if a case is satisfied and break statement is present then following cases are not checked.

 public class Test { public static void main(String args[]) { char grade = 'C'; switch(grade) { case 'A' : System.out.println("Excellent!"); break; case 'B' : case 'C' : System.out.println("Well done"); break; case 'D' : System.out.println("You passed"); case 'F' : System.out.println("Better try again"); break; default : System.out.println("Invalid grade"); } System.out.println("Your grade is " + grade); } } 

Compile and run the above program using various command line arguments. This will produce the following result −

Output

 Well done Your grade is C 

Example 2

In this example, we're showing use of switch statement where cases are based on a int. We've created a variable grade. Based on value of grade, each case is checked. if a case is satisfied and break statement is present then following cases are not checked.

 public class Test { public static void main(String args[]) { int grade = 3; switch(grade) { case 1 : System.out.println("Excellent!"); break; case 2 : case 3 : System.out.println("Well done"); break; case 4 : System.out.println("You passed"); case 5 : System.out.println("Better try again"); break; default : System.out.println("Invalid grade"); } System.out.println("Your grade is " + grade); } } 

Output

Compile and run the above program using various command line arguments. This will produce the following result −

 Well done Your grade is 3 

Example 3

In this example, we're showing use of switch statement where cases are based on a String. We've created a variable grade. Based on value of grade, each case is checked. if a case is satisfied and break statement is present then following cases are not checked.

 public class Test { public static void main(String args[]) { String grade = "C"; switch(grade) { case "A" : System.out.println("Excellent!"); break; case "B" : case "C" : System.out.println("Well done"); break; case "D" : System.out.println("You passed"); case "F" : System.out.println("Better try again"); break; default : System.out.println("Invalid grade"); } System.out.println("Your grade is " + grade); } } 

Output

Compile and run the above program using various command line arguments. This will produce the following result −

 Well done Your grade is C