jdk/test/langtools/tools/javac/enum/FauxEnum3.java

/*
 * @test /nodynamiccopyright/
 * @bug 5009574
 * @summary verify an enum type can't be directly subclassed
 *
 * @compile/fail/ref=FauxEnum3.out -XDrawDiagnostics  FauxEnum3.java
 */

public final class FauxEnum3 extends SpecializedEnum {}

enum SpecializedEnum {
    RED {
        boolean special() {return true;}
    },
    GREEN,
    BLUE;
    boolean special() {return false;}
}