How to separate a List by a condition using Java 8 streams

Question

Consider the following code:

 List odd = new ArrayList();
 List even = null;  
 List myList = Arrays.         


        

Answer 1

Here is an example of how you could separate elements (numbers) of this list in even and odd numbers:

List<Integer> myList = Arrays.asList(1,2,3,4,5,6,7,8,9,10);

Map<Boolean, List<Integer>> evenAndOdds = myList.stream()
        .collect(partitioningBy(i -> i % 2 == 0));

You would get lists of even/odd numbers like this (either list may be empty):

List<Integer> even = evenAndOdds.get(true);
List<Integer> odd = evenAndOdds.get(false);

You could pass any lambda with required logic in partitioningBy.