Java Enum instantiation

Question

public enum FOO{
    TATA(TOTO,TITI);

    public FOO(BAR bar1,BAR bar2) {
        bar1.associate(this,bar2);
    }
}

public enum BAR {
    TOTO,
    TITI;

    private FOO _foo;
    private BAR _bar;

    public void associate(FOO foo,BAR bar) {
        _foo = foo;
        _bar = bar;
    }
}

The problem was that in my code I called BAR before FOO. The result was the fields in BAR were null. I finally found out why. (enum are only instantiated when they are called for the first time). To fix this problem I added FOO.TATA; before I use Bar in a specific file.

So my question, Is there a more elegant way to make sure one enum is instantiate before another?

What do these enum represent in real life? It seems it's not very good place to use enums. — Mikita Belahlazau
– Mikita Belahlazau, Commented May 29, 2012 at 16:39
@NikitaBeloglazov it being use in a factory.. and unfortunately I don't have my word to say on this matter. — Jean-Christophe Fortin
– Jean-Christophe Fortin, Commented May 29, 2012 at 16:43

JB Nizet · Accepted Answer · 2012-05-29 16:52:54Z

2

Since they're closely related to each other, I would put them in the same class, that would play the role of a mediator:

public class FooBar {
    static {
        Bar.TOTO.associate(Foo.TATA, Bar.TITI);
    }

    public enum Foo {
        TATA;
    }

    public enum Bar {
        TOTO,
        TITI;

        private Foo _foo;
        private Bar _bar;

        private void associate(Foo foo, Bar bar) {
            _foo = foo;
            _bar = bar;
        }

        public Foo getFoo() {
            return _foo;
        }

        public Bar getBar() {
            return _bar;
        }
    }

    public static void main(String[] args) {
        System.out.println(FooBar.Bar.TITI.getFoo());
        System.out.println(FooBar.Bar.TITI.getBar());
        System.out.println(FooBar.Bar.TOTO.getFoo());
        System.out.println(FooBar.Bar.TOTO.getBar());
    } 
}

answered May 29, 2012 at 16:52

JB Nizet

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1 Comment

Jean-Christophe Fortin Over a year ago

Thanks, It's not exactly what I've done but I give me good idea !

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