Java Commons Collections removeAll

Edit January 1, 2014 Apache Commons Collections 4.0 was finally released on November 21, 2013, and contains a fix for this issue.

Link to CollectionUtils.java

Lines in question (1688 – 1691), with acknowledgement the method was previously broken:

/*
 ...
 * @since 4.0 (method existed in 3.2 but was completely broken)
 */
public static <E> Collection<E> removeAll(final Collection<E> collection, final Collection<?> remove) {
    return ListUtils.removeAll(collection, remove);
}

Original Answer

Nope, you’re not crazy. removeAll() is actually (incorrectly) calling retainAll().

This is a bug in CollectionUtils, affecting version 3.2. It’s been fixed, but only in the 4.0 branch.

https://issues.apache.org/jira/browse/COLLECTIONS-349

And as further proof, here’s a link to the source code:

http://svn.apache.org/repos/asf/commons/proper/collections/tags/COLLECTIONS_3_2/src/java/org/apache/commons/collections/CollectionUtils.java

Check out this line:

public static Collection removeAll(Collection collection, Collection remove) {
    return ListUtils.retainAll(collection, remove);
}

Yep…broken!