Java ArrayList removeAll() Examples

The removeAll() method is present in java.util.ArrayList class.

It is used to remove all the elements from the arrays List.

syntax 


  public boolean removeAll(Collection c)

c: a collection that contained elements to be removed from this list.

This method throws java.lang.NullPointerException: If the specified collection is null, or if the original list contains null elements and the specified collection does not permit null elements. 


import java.util. * ;

public class ArrylistRemoveAll {
	public static void main(String[] argv) throws Exception {

		try {

			ArrayList < String > arrlist1 = new ArrayList < String > ();

			arrlist1.add("January");
			arrlist1.add("February");
			arrlist1.add("March");
			arrlist1.add("April");
			arrlist1.add("May");

			System.out.println("ArrayList before " + "removeAll() operation : " + arrlist1);

			ArrayList < String > arrlist2 = new ArrayList < String > ();

			arrlist2.add("January");
			arrlist2.add("February");
			arrlist2.add("March");
			arrlist2.add("April");
			arrlist2.add("May");

			arrlist2.add("June");

			arrlist2.add("July");

			arrlist2.add("August");

			arrlist2.add("Septmeber");

			arrlist2.add("October");

			arrlist2.add("November");

			arrlist2.add("December");

			System.out.println("Collection in which the elements to be  removed  : ");
			System.out.println(arrlist2);
			arrlist2.removeAll(arrlist1);

			System.out.println("ArrayList after using removeAll operation: ");

			System.out.println(arrlist1);
		}

		catch(NullPointerException ex) {
			System.out.println("Exception occured during removing elements from ArrayList: " + ex);
		}
	}

}

output:
ArrayList before removeAll() operation : [January, February, March, April, May]
Collection in which the elements to be  removed  : 
[January, February, March, April, May, June, July, August, Septmeber, October, November, December]
ArrayList after using removeAll operation: 
[January, February, March, April, May]

Remove null from the ArrayList using removeAll

When we try to remove the null collection from the ArrayList we will get NullPointerException. 

 
import java.util.*;

public class ArrylistRemoveAllNull {
	public static void main(String[] argv) throws Exception {

		try {

			ArrayList < String > arrlist1 = new ArrayList < String > ();

			arrlist1.add("January");
			arrlist1.add("February");
			arrlist1.add("March");
			arrlist1.add("April");
			arrlist1.add("May");

	 
			System.out.println("ArrayList before " + "removeAll() operation : " + arrlist1);

 
			ArrayList  arrlist2 =  null;

		 
 
			System.out.println("Collection in which the elements to be  removed  : "
							); 
             System.out.println(arrlist2);
			arrlist2.removeAll(arrlist1); 
 
			System.out.println("ArrayList after using removeAll operation: "
							); 
							
							 System.out.println(arrlist1);
		} 

		catch (NullPointerException ex) { 
			System.out.println("Exception occured during removing elements from ArrayList: " + ex); 
		} 
	}

}

  output:
  ArrayList before removeAll() operation : [January, February, March, April, May]
Collection in which the elements to be  removed  : 
null
Exception occured during removing elements from ArrayList: java.lang.NullPointerException

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In this article, we have seen  Java ArrayList removeAll() Examples. All source code in the article can be found in the GitHub repository.