[jira] [Resolved] (COLLECTIONS-747) MultiKey.getKeys class cast exception

["Gary D. Gregory (Jira)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/COLLECTIONS-747?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Gary D. Gregory resolved COLLECTIONS-747.
-----------------------------------------
    Fix Version/s: 4.5
         Assignee: Gary D. Gregory
       Resolution: Fixed

[~wlaan],

Please checkout git master and check that the fix works for you,

Thank you!

> MultiKey.getKeys class cast exception
> -------------------------------------
>
>                 Key: COLLECTIONS-747
>                 URL: https://issues.apache.org/jira/browse/COLLECTIONS-747
>             Project: Commons Collections
>          Issue Type: Bug
>          Components: KeyValue
>    Affects Versions: 4.4
>            Reporter: Walter Laan
>            Assignee: Gary D. Gregory
>            Priority: Major
>             Fix For: 4.5
>
>
> When using an non-array constructor of MultiKey, an Object[] is created, which cannot be cast to a K[]
> {code}
> 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)
> {code}
> 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.
> {code}
>     @SafeVarargs
>     public MultiKey(K... keys) {
>         this.keys = keys;
>     }
> {code}
> Workaround is to use array constructor with correct typed array or {code}Object[] keys = multiKey.getKeys();{code} explicitly.



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