Accessing enum members from enum Class literal

Question

I'm using enums to provide a configuration framework. They work well, but I've hit a problem. This may be a bad use-case or just end up as a limitation of the enum support.
In a nutshell I want to return the enum container type from a method and allow clients to access the members of that enum directly. For example:
interface Widget
  Class<?> getColours();
class MyWidget implements Widget
  enum COLOUR { RED, GREEN, BLUE };
  public Class<COLOUR> getColours() { return COLOUR.class;}
// client
MyWidget w = new MyWidget();
w.setColour( w.getColours().BLUE ); // compile error!Of course, this gives a compile error as getColours() returned a class literal which doesn't have the field BLUE. However it seems like there should be a way to do this as all the information is there (the class literal has the necessary type information and can see the type is an enum). I've see Class#getEnumConstants() but this defeats the point by using an id or key to the enum rather than the enum member. Perhaps something like Class#asEnum():
COLOUR b = w.getColours().asEnum().BLUE;I currently solve this by using naming conventions. Each widget implementer is required (by the framework) to provide an enum with the name 'COLOUR' that provides the colours it supports. However I'd prefer to have this on the interface to remind implementers to expose these configuration options.
One other workaround is to create a custom container that holds a reference to each enum field ... but its not pretty:
class MyWidget implements Widget
  public static class COLOURS
    private static COLOURS instance = new COLOURS();
    private COLOURS() {}
    public COLOUR RED = COLOR.RED;
    public COLOUR BLUE = COLOR.BLUE;   
    public COLOUR GREE = COLOR.GREEN;
    enum COLOUR { RED, GREEN, BLUE };
  public COLOURS getColours() { return COLOURS.instance;}
// client
MyWidget w = new MyWidget();
w.setColour( w.getColours().BLUE ); // OKHas anyone hit this before and found a better solution? Is there something I've missed? If not does this seem like a reasonable request for improvement?

Answer 1

I suspect you're better off using the static values() or valueOf(String) methods on the enum you create.
So you could do
Colour c = Colour.valueOf("BLUE");or even
Color particularColour = null;
for(Colour c : Colour.values()) {
    if (c.isApplicable(someCriteria)) {
        particularColour = c;
        break;
}assuming you created a method isApplicable in the Colour enum. All I'm trying to suggest in this latter example is that selection of an enum value might be better delegated to the enum than performed by the caller.