Java - case Keyword

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