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Can I add and remove elements of enumeration at runtime in Java

Asked 2009-01-25T22:08:54.293
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It is possible to add and remove elements from an enum in Java at runtime?

For example, could I read in the labels and constructor arguments of an enum from a file?

@saua, it's just a question of whether it can be done out of interest really. I was hoping there'd be some neat way of altering the running bytecode, maybe using BCEL or something. I've also followed up with this question because I realised I wasn't totally sure when an enum should be used.

I'm pretty convinced that the right answer would be to use a collection that ensured uniqueness instead of an enum if I want to be able to alter the contents safely at runtime.

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I needed to do something like this (for unit testing purposes), and I came across this - the EnumBuster: http://www.javaspecialists.eu/archive/Issue161.html

It allows enum values to be added, removed and restored.

Edit: I've only just started using this, and found that there's some slight changes needed for java 1.5, which I'm currently stuck with:

  • Add array copyOf static helper methods (e.g. take these 1.6 versions: http://www.docjar.com/html/api/java/util/Arrays.java.html)
  • Change EnumBuster.undoStack to a Stack<Memento>
    • In undo(), change undoStack.poll() to undoStack.isEmpty() ? null : undoStack.pop();
  • The string VALUES_FIELD needs to be "ENUM$VALUES" for the java 1.5 enums I've tried so far
answered 2010-03-15T11:56:07.210

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