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switch

By · Reviewed & last updated · Part of Java Tutorial

Modern Java switch is an EXPRESSION that returns a value. Arrow syntax avoids fall-through; multiple labels per case; pattern matching (Java 21+) destructures records and types.

Switch expression + pattern matching

EXAMPLE
public class Demo {
    sealed interface Shape permits Circle, Rect, Triangle {}
    record Circle(double r) implements Shape {}
    record Rect(double w, double h) implements Shape {}
    record Triangle(double base, double height) implements Shape {}

    public static void main(String[] args) {
        var day = "Sat";

        // 1) Switch EXPRESSION — returns a value, no break needed
        var kind = switch (day) {
            case "Sat", "Sun"                          -> "weekend";
            case "Mon", "Tue", "Wed", "Thu", "Fri"      -> "weekday";
            default                                       -> "unknown";
        };
        System.out.println(kind);

        // 2) Block bodies + yield
        int score = 85;
        String grade = switch (score / 10) {
            case 10, 9 -> "A";
            case 8     -> {
                System.out.println("close to A");
                yield "B";
            }
            case 7     -> "C";
            default    -> "F";
        };

        // 3) Pattern matching — destructure records (Java 21+)
        Shape shape = new Circle(2.0);
        double area = switch (shape) {
            case Circle c               -> Math.PI * c.r() * c.r();
            case Rect r                 -> r.w() * r.h();
            case Triangle t when t.height() > 0 -> 0.5 * t.base() * t.height();
            case Triangle t              -> 0;
        };
        System.out.printf("area %.2f%n", area);

        // 4) Sealed types — compiler enforces exhaustiveness
        // If you add a new permits-class without updating this switch,
        // the compile FAILS — impossible to forget.
    }
}

Why it matters

Switch expressions on sealed types is THE pattern for modern Java domain logic. The compiler proves you handled every case — impossible states become impossible.

Tip: Tweak the snippet with Try it Yourself », then sit the quiz at the bottom of the page.

Example

Example
String day = "SAT";
String kind = switch (day) {
    case "SAT", "SUN" -> "weekend";
    default -> "weekday";
};
System.out.println(kind);
Try it Yourself »

Discussion

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