Is there a way to check if two Collections contain the same elements, independent of order?
collections, equals, java
Solution
Apache commons-collections has CollectionUtils#isEqualCollection:
Returns true if the given Collections contain exactly the same elements with exactly the same cardinality.
That is, if the cardinality of e in a is equal to the cardinality of e in b, for each element e in a or b.
Which is, I think, exactly what you're after.
Problem
I've been looking for a method that operates like `Arrays.equals(a1, a2)`, but ignoring the element order. I haven't been able to find it in either Google Collections (something like `Iterables.elementsEqual()`, but that does account for ordering) and JUnit (`assertEquals()` obviously just calls `equals()` on the Collection, which depends on the Collection implementation, and that's not what I want) It would be best if such a method would take `Iterable`s, but I'm also fine with simply taking `Collection`s Such a method would of course take into account any duplicate elements in the collection (so it can't simply test for `containsAll()`). Note that I'm not asking how to implement such a thing, I was just wondering if any of the standard Collections libraries have it.