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From "Thomas Neidhart (JIRA)" <>
Subject [jira] [Resolved] (COLLECTIONS-394) FastTreeMap is not compatible with TreeMap
Date Sat, 23 Jun 2012 17:14:42 GMT


Thomas Neidhart resolved COLLECTIONS-394.

       Resolution: Won't Fix
    Fix Version/s: 4.0

The FastTreeMap class has been removed from trunk.

There is no drop-in replacement, but one can use a ConcurrentHashMap from the java.util.concurrent
package or a synchronized TreeMap.

Please open new issue if you would like to have an equivalent class in collections 4.0.
> FastTreeMap is not compatible with TreeMap
> ------------------------------------------
>                 Key: COLLECTIONS-394
>                 URL:
>             Project: Commons Collections
>          Issue Type: Bug
>          Components: Map
>    Affects Versions: 3.2.1
>         Environment: all
>            Reporter: Michael Pradel
>             Fix For: 4.0
> FastTreeMap extends TreeMap in a way that doesn't preserve the superclass behavior. For
example, the following code prints 'null', but I would expect it to print '1=1', which is
what TreeMap does:
> TreeMap map = new FastTreeMap();
> //TreeMap map = new TreeMap();
> map.put(1, "1");
> map.put(3, "3");
> Entry e = map.floorEntry(2);
> System.out.println(e);
> This behavior is surprising and can hit you every time a reference of type TreeMap refers
to an instance of FastTreeMap. A subclass instance used through a superclass interface shouldn't
change the visible behavior of its superclass.
> The reason for this problem seems to be that FastTreeMap both extends TreeMap and delegates
to a TreeMap via the 'map' field. I.e., there are  two map instances for a single FastTreeMap

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