ArrayList removeAll() method in Java with Examples

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