Java 8 stream. all elements EXCEPT other elements

Question

I'm interested in identifying an approach that returns a list of elements excluding the elements in another list.

for example

List<Integer> multiplesOfThree = ... // 3,6,9,12 etc List<Integer> evens = ... // 2,4,6,8 etc List<Integer> others = multiplesOfThree.except(evens) // should return a list of elements that are not in the other list 

how do you do this? i found an approach that's a bit clunky and difficult to read....

multiplesOfThree.stream() .filter(intval -> evens.stream().noneMatch(even -> even.intValue() == intval.intValue())) 

Answer 1

You can use Stream's filter method, passing a Predicate that ensures that the element doesn't exist in evens.

List<Integer> others = multiplesOfThree.stream()         .filter(i -> !evens.contains(i))         .collect(Collectors.toList()); 

But assuming you have a mutable List (e.g. ArrayList), you don't even need streams, just Collections's removeAll method.

multiplesOfThree.removeAll(evens);