Union and Intersection of ArrayList in Java

import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;

public class Main
{

    public static void main(String[] args)
    {

         List<String> list1 = new ArrayList<String>(Arrays.asList("A", "B", "C"));
         List<String> list2 = new ArrayList<String>(Arrays.asList("B", "C", "D", "E", "F"));

          list1.retainAll(list2) ;

          System.out.println(list1);
          System.out.println(list2);         
    }
}

[B, C]
[B, C, D, E, F]

import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;

public class Main
{

    public static void main(String[] args)
    {

         List<String> list1 = new ArrayList<String>(Arrays.asList("A", "B", "C"));
         List<String> list2 = new ArrayList<String>(Arrays.asList("B", "C", "D", "E", "F"));

          list1.addAll(list2) ;

          System.out.println(list1);
          System.out.println(list2);         
    }
}

[A, B, C, B, C, D, E, F]
[B, C, D, E, F]