Switch on enum (with examples)

Java has support for switching on enum values.

 Full contextswitch (month) {
    case FEB:
        System.out.println("28 days");
        break;
    case APR:
    case JUN:
    case SEP:
    case NOV:
        System.out.println("30 days");
        break;
    default:
        System.out.println("31 days");
}enum Month {
    JAN, FEB, MAR, APR, MAY, JUN,
    JUL, AUG, SEP, OCT, NOV, DEC
}

public class EnumDemo {
    static void printNumDays(Month month) {
        switch (month) {
            case FEB:
                System.out.println("28 days");
                break;
            case APR:
            case JUN:
            case SEP:
            case NOV:
                System.out.println("30 days");
                break;
            default:
                System.out.println("31 days");
        }
    }

    public static void main(String[] args) {
        printNumDays(Month.FEB); // 28 days
        printNumDays(Month.JUN); // 30 days
        printNumDays(Month.DEC); // 31 days
    }
}

You must not fully qualify the constants. This will not compile: case Month.FEB: …

Arrow Syntax

With Java 14+ the above switch statement can be written as:

static void printNumDays(Month month) {
    switch (month) {
        case FEB -> System.out.println("28 days");
        case APR, JUN, SEP, NOV -> System.out.println("30 days");
        default -> System.out.println("31 days");
    }
}

Or using a switch expression:

static void printNumDays(Month month) {
    int days = switch (month) {
        case FEB -> 28;
        case APR, JUN, SEP, NOV -> 30;
        default -> 31;
    };
    System.out.println(days + " days");
}

See Switch Statement and Switch Expression for more examples.