Pattern matching for switch

Definition

Pattern matching for switch (Java 21) lets a switch choose code by the type of a value, and even add a condition with when. It also handles null as a case.

Example code

A switch that picks code by type and condition

class Demo {
    static String describe(Object value) {
        return switch (value) {
            case null -> "nothing";
            case Integer i when i > 100 -> "a big number: " + i;     // type plus a condition
            case Integer i -> "a number: " + i;
            case String s -> "text of length " + s.length();
            default -> "something else";
        };
    }

    public static void main(String[] args) {
        System.out.println(describe(500));
        System.out.println(describe(7));
        System.out.println(describe("java"));
        System.out.println(describe(null));
        System.out.println(describe(2.5));
    }
}

// Output:
// a big number: 500
// a number: 7
// text of length 4
// nothing
// something else