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https://issues.apache.org/jira/browse/COLLECTIONS-747?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17034192#comment-17034192
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Chen Guoping commented on COLLECTIONS-747:
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Can you using it follow the JAVADoc ?
[http://commons.apache.org/proper/commons-collections/apidocs/org/apache/commons/collections4/keyvalue/MultiKey.html]
K[] getKeys()K[] getKeys()Gets a clone of the array of keys.
> 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
> Priority: Major
>
> 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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