Intersection and union of ArrayLists in Java

Question

Are there any methods to do so? I was looking but couldn\'t find any.

Another question: I need these methods so I can filter files. Some are AND filter

Answer 1

I think you should use a Set to hold the files if you want to do intersection and union on them. Then you can use Guava's Sets class to do union, intersection and filtering by a Predicate as well. The difference between these methods and the other suggestions is that all of these methods create lazy views of the union, intersection, etc. of the two sets. Apache Commons creates a new collection and copies data to it. retainAll changes one of your collections by removing elements from it.