Why is default required for a switch on an enum?

Question

Normally, default is not necessary in a switch statement. However, in the following situation the code successfully compiles only when I uncomment the default statement. Can

Answer 1

In Java 12 you can use the preview switch expression feature (JEP-325) as follows:

public static String testSwitch(XYZ xyz) {
    return switch (xyz) {
        case A -> "A";
        case B -> "B";
    };
}

and you don't need default case as long as you handle all enum values in switch.

Note, to use a preview feature you'll have to pass --enable-preview --source 12 options to javac and java