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Null Pointer Exception - ANTLR TreeWalker

I keep getting a NullPoiterException in my TreeWalker but I can't seem to find out why.

I can't post the whole grammar, cause it's far too long.

This is the rule in the treeWalker where antlrWorks says the problem is:

collection_name returns [MyType value]
    : ID { $value = (MyType) database.get($collection_name.text); }
    ;

Note that database is a HashMap.

Thank you!

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  • Yes, you are right ,I obviously did not poste enough code. Anyway, that is not the problem. The problem is that somehow my AST is not parsed how it should be.
    – user1550876
    Commented Aug 22, 2012 at 17:36
  • The problem was that in a treeGrammar you can't do something like $collection_name.text , as you would in a parser grammar. That was the whole problem. I spent hours thinking my AST is wrong and trying to fix it. Thank you for your help!
    – user1550876
    Commented Aug 22, 2012 at 23:21
  • @user1550876, cool, I somehow read over the fact that it was a tree tree! Good to hear you resolved it.
    – Bart Kiers
    Commented Aug 23, 2012 at 6:24