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Alex
Alex

Reputation: 2976

Java: How to get Values of an Enum Class from an Generic Type Object instance?

I want to create an Enum editor, which takes an Enum type as its generic. E is a generic type, but restricted to be an Enum type. How can I get the values of the Enum class from the instance e?

public class ComboBoxEnumEditor<E extends Enum<E>>{
    public ComboBoxEnumEditor(E e) {
        // how to get values of E from e?
        // attemp1:
        List values = e.getClass().values();
        // attemp2:
        List values = ((Enum.class)e.getClass()).values();
        // attemp3:
        List values = ((Enum.class)e.getClass()).values();
        // none of the above works... 
    }
}

Say I have an Enum

public enum Location {
    Default( false, EAttributeLocation.MAIN_TABLE_IF_AVAILABLE ),
    Main( false, EAttributeLocation.MAIN_TABLE ),
    Overflow( false, EAttributeLocation.OVERFLOW_TABLE ),
    Separate( false, EAttributeLocation.SEPARATE_TABLE );
    ......
}

I want my ComboBoxEnumEditor be able to do

{
   ComboBoxEnumEditor(new Location());
}

Please help, thanks.

Upvotes: 4

Views: 4890

Answers (3)

Pshemo
Pshemo

Reputation: 124275

It looks like you are looking for (but I may be mistaken)

Enum[] values = e.getClass().getEnumConstants();

or as mentioned by @pbabcdefp in this answer (big +1 for him) if you would like to have E[] instead of Enum[] 

E[] values = e.getDeclaringClass().getEnumConstants();

Also based on

...which takes an Enum Class as its generic

your argument should probably be Class<E> clazz not E e itself so you could use it with ComboBoxEnumEditor(Location.class);. In that case you could simply use

E[] values = clazz.getEnumConstants();

Upvotes: 14

Necreaux
Necreaux

Reputation: 9786

Short answer... You can't. Doing this is not valid syntax since you can't instantiate an enum:

ComboBoxEnumEditor(new Location());

Instead, you need to pass the class of your enum and change your method signature for that, e.g.

ComboBoxEnumEditor(Location.class);

Upvotes: 0

Paul Boddington
Paul Boddington

Reputation: 37655

E[] arr = e.getDeclaringClass().getEnumConstants();

Upvotes: 5

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