Re: enum paralellism

From:

Daniel Pitts <newsgroup.nospam@virtualinfinity.net>

Newsgroups:

comp.lang.java.programmer

Date:

Tue, 17 Jan 2012 10:34:55 -0800

Message-ID:

<kbjRq.962$744.661@newsfe10.iad>

On 1/16/12 6:16 AM, Roedy Green wrote:

What if you have two enum classes that have similar structure, e.g.
similar method names, similar instance variables or similar enum
constants.

Is there any way to specify that similarity in one place or to use
interfaces, abstract classes, EnumSets or inheritance to enforce the
parallel structure? I have not found a way.

Enums can implement interfaces:

public enum MyEnum implements Runnable {
    A { public void run() { System.out.println("A Runs!"); } },
    B { public void run() { System.out.println("B is an also ran."); } }
    ;
}

But they can not extend other classes. Enum *constants* however
automatically extend the (automatically abstract) Enum class. So you can
have abstract methods in the base enum class.

public enum MyEnum {
    A { public void run() { System.out.println("A Runs!"); } },
    B { public void run() { System.out.println("B is an also ran."); } }
    ;

    public abstract void run();
}

It sounds like you want a combination of abstract methods and interfaces.