Java Language Tutorial => Finding common elements between 2 lists

Example

Suppose you have two lists: A and B, and you need to find the elements that exist in both lists.

You can do it by just invoking the method List.retainAll().

Example:

public static void main(String[] args) {
    List<Integer> numbersA = new ArrayList<>();
    List<Integer> numbersB = new ArrayList<>();
    numbersA.addAll(Arrays.asList(new Integer[] { 1, 3, 4, 7, 5, 2 }));
    numbersB.addAll(Arrays.asList(new Integer[] { 13, 32, 533, 3, 4, 2 }));

    System.out.println("A: " + numbersA);
    System.out.println("B: " + numbersB);
    List<Integer> numbersC = new ArrayList<>();
    numbersC.addAll(numbersA);
    numbersC.retainAll(numbersB);

    System.out.println("List A : " + numbersA);
    System.out.println("List B : " + numbersB);
    System.out.println("Common elements between A and B: " + numbersC);

}

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