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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Java13: Switch expression

From Java 13 onward, you can use switch statement either as a statement or an expression (This feature is already available in Java12 preview mode).

 

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

 

SwitchExpressionDemo1.java

package com.sample.app.switchexp;

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

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

		System.out.println(result);
	}

}

 

Output

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/354

 

 

 

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Java12: Switch expression(Preview mode)

Java12 introduces switch expression feature in preview mode. From Java12 onwards, you can use switch statement either as a statement or an expression.

 

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

 

Prior to Java12

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");
}

 

From Java12 onwards, you can use switch as expression like below.

 

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";
};

Find the below working application.

 

SwitchExpressionExample.java

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

		// Prior to Java12
		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");
		}

		// From Java12
		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);
	}

}

How to compile SwitchExpressionExample application?

javac --release 12 --enable-preview SwitchExpressionExample.java

 

How to run SwitchExpressionExample?

java --enable-preview SwitchExpressionExample

 

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 break statement.

 

SwitchExpressionExample2.java

public class SwitchExpressionExample2 {
	public static void main(String args[]) {
		int number = 2;

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

		System.out.println(result);
	}

}

Output

$javac --release 12 --enable-preview SwitchExpressionExample2.java 
Note: SwitchExpressionExample2.java uses preview language features.
Note: Recompile with -Xlint:preview for details.
$
$
$java --enable-preview SwitchExpressionExample2
For input 2
Number is even and prime

Reference

https://openjdk.java.net/jeps/325

 

 

 

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