Chapter 6:Java Switch Statement and Array Basics

Switch Statement in java

Switch statement is used to select one of many code blocks to be executed.

Syntax

switch(expression) {
  case x:
    // code block
    break;
  case y:
    // code block
    break;
  default:
    // code block
}

This is how it works:

• The switch expression is evaluated once.
• The value of the expression is compared with the values of each case.
• If there is a match, the associated block of code is executed.
• The break and default keywords are optional, and will be described later in this chapter

The example below uses the weekday number to calculate the weekday name:

Example

public class SwitchDemo {

	public static void main(String[] args) {
		int Month = 11;
		switch (Month) {
		case 1:
			System.out.println("January");
			break;
		case 2:
			System.out.println("February");
			break;
		case 3:
			System.out.println("March");
			break;
		case 4:
			System.out.println("April");
			break;
		case 5:
			System.out.println("May");
			break;
		case 6:
			System.out.println("June");
			break;
		case 7:
			System.out.println("July");
			break;
		case 8:
			System.out.println("August");
			break;
		case 9:
			System.out.println("September");
			break;
		case 10:
			System.out.println("October");
			break;
		case 11:
			System.out.println("November");
			break;
		case 12:
			System.out.println("December");
			break;
		}

	}

}

Output:

November

The break Keyword

When Java reaches a break keyword, it breaks out of the switch block.

This will stop the execution of more code and case testing inside the block.

When a match is found, and the job is done, it’s time for a break. There is no need for more testing.

A break can save a lot of execution time because it “ignores” the execution of all the rest of the code in the switch block.

The default Keyword

The default keyword inform some code to run if there is no case match:

Example

public class SwitchDemo {

	public static void main(String[] args) {
		int Month = 13;
		switch (Month) {
		case 1:
			System.out.println("January");
			break;
		case 2:
			System.out.println("February");
			break;
		case 3:
			System.out.println("March");
			break;
		case 4:
			System.out.println("April");
			break;
		case 5:
			System.out.println("May");
			break;
		case 6:
			System.out.println("June");
			break;
		case 7:
			System.out.println("July");
			break;
		case 8:
			System.out.println("August");
			break;
		case 9:
			System.out.println("September");
			break;
		case 10:
			System.out.println("October");
			break;
		case 11:
			System.out.println("November");
			break;
		case 12:
			System.out.println("December");
			break;
		default:
		    System.out.println("This is an Invalide Month");
		}

	}

}

Output:

 This is an Invalide Month

Note that if the default statement is used as the last statement in a switch block, it does not need a break.

For more detail and practice , please see this video –