The implementation of version 3.2.1 is
public static Collection subtract(final Collection a, final Collection b) {
ArrayList list = new ArrayList( a );
for (Iterator it = b.iterator(); it.hasNext()
{
list.remove(it.next());
}
return list;
}
when a and b are large and similar the subtract implementation will call ArrayList.remove() frequently which copies a potentially large part of the list using system.arraycopy.
Suggestion : use LinkedList ( at least for large lists )
Improvement
Closed
Minor
CollectionUtils.subtract() should not use ArrayList to improve speed
