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  1. Commons Collections
  2. COLLECTIONS-747

MultiKey.getKeys class cast exception

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    Details

    • Type: Bug
    • Status: Resolved
    • Priority: Major
    • Resolution: Fixed
    • Affects Version/s: 4.4
    • Fix Version/s: 4.5
    • Component/s: KeyValue
    • Labels:
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      Description

      When using an non-array constructor of MultiKey, an Object[] is created, which cannot be cast to a K[]

      import org.apache.commons.collections4.keyvalue.MultiKey;
      
      public class MultiKeyClassCastException {
      
          public static void main(String[] args) {
              MultiKeyClassCastException key1 = new MultiKeyClassCastException();
              MultiKeyClassCastException key2 = new MultiKeyClassCastException();
              MultiKeyClassCastException[] keys = new MultiKey<>(key1, key2).getKeys();
          }
      }
      
      // running gives (same error if in module):
      
      Exception in thread "main" java.lang.ClassCastException: class [Ljava.lang.Object; cannot be cast to class [LMultiKeyClassCastException; ([Ljava.lang.Object; is in module java.base of loader 'bootstrap'; [LMultiKeyClassCastException; is in unnamed module of loader 'app')
      	at MultiKeyClassCastException.main(MultiKeyClassCastException.java:8)
      

      AFAIK, the only way to fix this (with source compatibility), is to only have a varargs constructors. but I think this breaks binary compatibility though and cannot be used with the existing constructors.

          @SafeVarargs
          public MultiKey(K... keys) {
              this.keys = keys;
          }
      

      Workaround is to use array constructor with correct typed array or

      Object[] keys = multiKey.getKeys();

      explicitly.

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            • Assignee:
              ggregory Gary D. Gregory
              Reporter:
              wlaan Walter Laan
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                Updated:
                Resolved: