The removeAll() method of java.util.ArrayList class is used to remove from this list all of its elements that are contained in the specified collection.
Syntax:
public boolean removeAll(Collection c)
Parameters: This method takes collection c as a parameter containing elements to be removed from this list.
Returns Value: This method returns true if this list changed as a result of the call.
Exception: This method throws NullPointerException if this list contains a null element and the specified collection does not permit null elements (optional), or if the specified collection is null.
Below are the examples to illustrate the removeAll() method.
Example 1:
Java
// Java program to demonstrate// removeAll() method for Integer value  import java.util.*;  public class GFG1 {    public static void main(String[] argv) throws Exception    {          try {              // Creating object of ArrayList<Integer>            ArrayList<Integer>                arrlist1 = new ArrayList<Integer>();              // Populating arrlist1            arrlist1.add(1);            arrlist1.add(2);            arrlist1.add(3);            arrlist1.add(4);            arrlist1.add(5);              // print arrlist1            System.out.println("ArrayList before "                               + "removeAll() operation : "                               + arrlist1);              // Creating another object of ArrayList<Integer>            ArrayList<Integer>                arrlist2 = new ArrayList<Integer>();            arrlist2.add(1);            arrlist2.add(2);            arrlist2.add(3);              // print arrlist2            System.out.println("Collection Elements"                               + " to be removed : "                               + arrlist2);              // Removing elements from arrlist            // specified in arrlist2            // using removeAll() method            arrlist1.removeAll(arrlist2);              // print arrlist1            System.out.println("ArrayList after "                               + "removeAll() operation : "                               + arrlist1);        }          catch (NullPointerException e) {            System.out.println("Exception thrown : " + e);        }    }} |
Output:
ArrayList before removeAll() operation : [1, 2, 3, 4, 5] Collection Elements to be removed : [1, 2, 3] ArrayList after removeAll() operation : [4, 5]
Example 2: For NullPointerException
Java
// Java program to demonstrate// removeAll() method for Integer value  import java.util.*;  public class GFG1 {    public static void main(String[] argv) throws Exception    {          try {              // Creating object of ArrayList<Integer>            ArrayList<Integer>                arrlist1 = new ArrayList<Integer>();              // Populating arrlist1            arrlist1.add(1);            arrlist1.add(2);            arrlist1.add(3);            arrlist1.add(4);            arrlist1.add(5);              // print arrlist1            System.out.println("ArrayList before "                               + "removeAll() operation : "                               + arrlist1);              // Creating another object of ArrayList<Integer>            ArrayList<Integer>                arrlist2 = null;              // print arrlist2            System.out.println("Collection Elements"                               + " to be removed : "                               + arrlist2);              System.out.println("\nTrying to pass "                               + "null as a specified element\n");              // Removing elements from arrlist            // specified in arrlist2            // using removeAll() method            arrlist1.removeAll(arrlist2);              // print arrlist1            System.out.println("ArrayList after "                               + "removeAll() operation : "                               + arrlist1);        }          catch (NullPointerException e) {            System.out.println("Exception thrown : " + e);        }    }} |
Output:
ArrayList before removeAll() operation : [1, 2, 3, 4, 5] Collection Elements to be removed : null Trying to pass null as a specified element Exception thrown : java.lang.NullPointerException
