CollectionUtils::removeAll() Commons Collections 3.2.1
I must be going crazy, becuase it seems like this method is doing the inverse of what the docs state:
Removes the elements in remove from collection. That is, this method returns a collection containing all the elements in c that are not in remove.
This little JUnit test
@Test
public void testCommonsRemoveAll() throws Exception {
String str1 = "foo";
String str2 = "bar";
String str3 = "qux";
List<String> collection = Arrays.asList(str1, str2, str3);
System.out.println("collection: " + collection);
List<String> remove = Arrays.asList(str1);
System.out.println("remove: " + remove);
Collection result = CollectionUtils.removeAll(collection, remove);
System.out.println("result: " + result);
assertEquals(2, result.size());
}
Is failing with
java.lang.AssertionError: expected:<2> but was:<1>
and prints
collection: [foo, bar, qux]
remove: [foo]
result: [foo]
From my reading of the docs I should expect [bar, qux]
. What have I missed?
Edit January 1, 2014 Apache Commons Collections 4.0 was finally released on November 21, 2013, and contains a fix for this issue.
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:
Check out this line:
public static Collection removeAll(Collection collection, Collection remove) {
return ListUtils.retainAll(collection, remove);
}
Yep...broken!