Java14: Switch expression

Switch expression is introduced as preview feature in Java12 and 13.

a.   Java12 First preview (https://openjdk.java.net/jeps/325)

b.   Java13 Second preview (https://openjdk.java.net/jeps/354)

 

In Java14, switch expressions are added as permanent feature (https://openjdk.java.net/jeps/361).

 

Switch expressions bring clear and safe code. Let us see it with an example.

 

Without switch expressions

switch (number) {
	case 2:
		System.out.println("Number is even and prime");
		break;
	case 3:
	case 5:
		System.out.println("You choosen a prime number and it is < 7");
		break;
	case 4:
	case 6:
		System.out.println("You entered even number and it is < 8.");
	
	default:
		System.out.println("You entered a number");
}

 

With switch expressions

String result = switch (number) {
	case 2 ->  "Number is even and prime";
	case 3, 5 -> "You choosen a prime number and it is < 7";
	case 4, 6 -> "You entered even number and it is < 8.";
	default -> "You entered a number";
};

SwitchExpressionDemo1.java

public class SwitchExpressionDemo1 {
	public static void main(String args[]) {
		int number = 2;

		// Without switch expression
		switch (number) {
		case 2:
			System.out.println("Number is even and prime");
			break;
		case 3:
		case 5:
			System.out.println("You choosen a prime number and it is < 7");
			break;
		case 4:
		case 6:
			System.out.println("You entered even number and it is < 8.");

		default:
			System.out.println("You entered a number");
		}

		// with switch expression
		String result = switch (number) {
			case 2 ->  "Number is even and prime";
			case 3, 5 -> "You choosen a prime number and it is < 7";
			case 4, 6 -> "You entered even number and it is < 8.";
			default -> "You entered a number";
		};
		
		System.out.println(result);
	}

}

Output

Number is even and prime

Number is even and prime

 

If your case statement has multiple lines, then enclose them in curly braces {} and return the last line using yield expression.

 

SwitchExpressionDemo2.java

public class SwitchExpressionDemo2 {
	public static void main(String args[]) {
		int number = 2;

		
		String result = switch (number) {
		case 2 -> {
			System.out.println("For input 2");
			yield "Number is even and prime";
		}
		case 3, 5 -> {
			System.out.println("For input 3 or 5");
			yield "You choosen a prime number and it is < 7";
		}
		case 4, 6 -> {
			System.out.println("For input 4 or 6");
			yield "You entered even number and it is < 8.";
		}
		default -> {
			System.out.println("No input matched");
			yield "You entered a number";
		}
	};

		System.out.println(result);
	}

}

Output

For input 2

Number is even and prime

 

1. As you see above snippet, value returned from switch expression is assigned to the variable ‘result’.

2. If you have multiple case statements that matches to same business logic, you can separate case conditions by comma operator.

 

Example

case 3, 5: yield "You choose a prime number and it is < 7";

 

 

Reference

https://openjdk.java.net/jeps/361

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