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Thread: Need help

  1. #1
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    Default Need help

    I've been studying for my OCP certification and I've come across something I don't understand.
    Note: the code below is non-sense and not meant to do anything real but rather to illustrate the behavior that I'm curious about. I would never write production code like this but I can't help but be puzzled as to why it works this way.

    The following code compiles w/o issue

     char end = 'z';
     String s = "";
     Predicate<Character> predicate = c -> {
       char start = 'a';
       return start <= c && c <= end;
     };
     char c = 'Z';
     char start = 'B';

    if I move the final two lines of that block above the predicate definition it doesn't compile and it instead complains that I'm attempting to redeclare c & start inside my predicate.

     char end = 'z';
     String s = "";
     char c = 'Z';
     char start = 'B';
     Predicate<Character> predicate = c -> {
       char start = 'a';
       return start <= c && c <= end;
     };

    I assume this is something about how Java deals with lambda methods but why does having the declarations for c & start before the predicate cause issues while having them below does not?

  2. #2
    Super Moderator Norm's Avatar
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    Default Re: Need help

    That problem was discussed here: https://www.coderanch.com/t/782694/j...plain-behavior
    If you don't understand my answer, don't ignore it, ask a question.