Remove all the elements from an ArrayList that are in another Collection in Java

The method java.util.ArrayList.removeAll() removes all the the elements from the ArrayList that are available in another collection. This method has a single parameter i.e. the Collection whose elements are to be removed from the ArrayList.

A program that demonstrates this is given as follows

Example

 Live Demo

import java.util.ArrayList;
import java.util.List;
public class Demo {
   public static void main(String args[]) throws Exception {
      List aList1 = new ArrayList();
      aList1.add("Anna");
      aList1.add("John");
      aList1.add("Mary");
      aList1.add("Amy");
      aList1.add("Harry");
      List aList2 = new ArrayList();
      aList2.add("John");
      aList2.add("Harry");
      aList2.add("Amy");
      aList1.removeAll(aList2);
      System.out.println("The elements in ArrayList aList1 are: " + aList1);
   }
}

The output of the above program is as follows

The elements in ArrayList aList1 are: [Anna, Mary]

Now let us understand the above program.

The ArrayLists aList1 and aList2 are created. Then ArrayList.add() is used to add the elements to both the ArrayList. A code snippet which demonstrates this is as follows

List aList1 = new ArrayList();
aList1.add("Anna");
aList1.add("John");
aList1.add("Mary");
aList1.add("Amy");
aList1.add("Harry");
List aList2 = new ArrayList();
aList2.add("John");
aList2.add("Harry");
aList2.add("Amy");

The ArrayList.removeAll() method is used to remove all the the elements from the aList1 that are available in aList2. Then the elements in aList1 are printed. A code snippet which demonstrates this is as follows

aList1.removeAll(aList2);
System.out.println("The elements in ArrayList aList1 are: " + aList1);