Thomas Vahrst created COLLECTIONS-441:
-----------------------------------------
Summary: MultiKeyMap.clone() should call super.clone()
Key: COLLECTIONS-441
URL: https://issues.apache.org/jira/browse/COLLECTIONS-441
Project: Commons Collections
Issue Type: Improvement
Components: Map
Affects Versions: 4.0-beta-1
Reporter: Thomas Vahrst
Priority: Minor
This issue addresses a findbugs issue:
{quote}
org.apache.commons.collections.map.MultiKeyMap.clone() does not call
super.clone()
{quote}
The current clone() implementation creates a new MultiKeyMap instance. This
will lead to problems when clone() is invoked on subclasses of MultiKeyMap.
This is a corresponding junit test which fails:
{code}
class MultiKeyMapTest
// Subclass to test clone() method
private static class MultiKeyMapSubclass extends MultiKeyMap<String,
String>{
}
public void testCloneSubclass(){
MultiKeyMapSubclass m = new MultiKeyMapSubclass();
m.put("A", "B", "C");
MultiKeyMapSubclass m2 = (MultiKeyMapSubclass) m.clone();
assertEquals("C", m.get("A", "B"));
}
{code}
Instead of creating a new MultiKeyMap instance, the clone() method should
invoke super.clone() which leads in Object.clone(). This always returns an
object of the correct type.
{code}
class MultiKeyMap{
/**
* Clones the map without cloning the keys or values.
*
* @return a shallow clone
*/
@Override
public MultiKeyMap<K, V> clone() {
try {
MultiKeyMap<K,V> m = (MultiKeyMap<K, V>) super.clone();
AbstractHashedMap<MultiKey<? extends K>, V> del =
(AbstractHashedMap<MultiKey<? extends K>, V>)decorated().clone();
m.map = del;
((AbstractMapDecorator<K,V>)m).map = (Map) del;
return m;
} catch (CloneNotSupportedException ex) {
throw new RuntimeException (ex); // this should never happen...
}
}
{code}
*Note*
For serialisation compatibilty reasons to commons collections V.3.2,
MultiKeyMap contains a map reference (the decorated map) which hides the same
field in the super class AbstractMapDecorator. This is quite 'ugly' to
understand and maintain.
Should we consider to break the compatibility to the 3.2 version?
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