What rule of thumb applies to Swing component expansion?

When you dedicate a class to a specific Swing component, is it better to extenduse that particular component or build it inside and provide a link?

public class Foo extends JComponent{

}

OR

public class Foo{
    public JComponent getComponent(){
    }
}

EDIT

This is what I mean by initiation.

public class Foo{
    private static Foo INSTANCE;

    public static Foo getInstance(){
        if(INSTANCE == null){
            INSTANCE = new Foo();
        }
    }

    public void createAndShowComponent(){
        //do stuff
    }
}

Inside, createAndShowComponent()I create JComponentwith all its components and their corresponding listeners without , displaying the internal components of the component just created.