Java 8 # duplicate elements in a given integer

 import java.util.*;

import java.util.stream.*;

public class DuplicateElements {
    public static void main(String[] args) {
        List<Integer> mylist = Arrays.asList(11, 11, 12, 12, 13,14);
        Set<Integer> myset = new HashSet();
        mylist.stream()
                .filter(n -> !myset.add(n))
                .forEach(System.out::println);
    }
}