Why "final static int" can be used as a switch's case constant but not "final static <your enum>"

Question

Why is this int switch valid:

public class Foo {
    private final static int ONE = 1;
    private final static int TWO = 2;

    public static void main(String[] args) {
        int value = 1;
        switch (value) {
            case ONE: break;
            case TWO: break;
        }
    }

}

While this enum switch is not:

import java.lang.annotation.RetentionPolicy;

public class Foo {
    private final static RetentionPolicy RT = RetentionPolicy.RUNTIME;
    private final static RetentionPolicy SRC = RetentionPolicy.SOURCE;

    public static void main(String[] args) {
        RetentionPolicy value = RetentionPolicy.RUNTIME;
        switch (value) {
            case RT: break;
            case SRC: break;
        }
    }

}

I know that what goes in the case must be a constant, so why can I use a "final static int" as constant but not a "final static <your enum>"?

Answer 1

Because a case statement label must have either a compile time constant or an EnumConstantName. JLS 14.11

Compile time constants can only be strings and primitive types, as described by JLS 15.28. Thus you can not use a static final <your enum>, as it is neither a compile time constant, nor the name of an enum.

Answer 2

The case argument must be primitive; it cannot be an object.

However, you can use enums as follows:

RetentionPolicy value = ...
switch (value) {
    case RUNTIME:
    case SOURCE:
}

Because value is declared to be of type RetentionPolicy you can use the enum constants directly inside the switch.