Remove one set from another set

 
import java.util.HashSet;
import java.util.Set;

public class Main {
  public static void main(String[] args) {
    Set<Integer> uniques = new HashSet<Integer>();
    Set<Integer> dups = new HashSet<Integer>();

    uniques.add(new Integer(1));
    uniques.add(new Integer(2));
    uniques.add(new Integer(3));
    uniques.add(new Integer(4));
    
    
    dups.add(new Integer(1));
    dups.add(new Integer(2));
    dups.add(new Integer(3));

    uniques.removeAll(dups);

    System.out.println("Unique words:    " + uniques);
    System.out.println("Duplicate words: " + dups);
  }
}
  

Unique words:    [4]
Duplicate words: [1, 2, 3]