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AbstractSet removeAll() Method in Java

Last Updated : 11 Jul, 2025
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The removeAll() method of the Java AbstractSet class is part of the Java Collections Framework. This method is used to remove all elements from the current set that are also contained in another collection or set.

Example 1: This example is used to remove all elements from the abstract set using the removeAll() method.

Java 
// Java program to demonstrate 
// removeAll() method for Integer value 
import java.util.*;

public class Geeks 
{
    public static void main(String[] args) throws Exception 
    {
        try 
        {        
            // Creating object of AbstractSet<Integer>
            AbstractSet<Integer> as = new TreeSet<Integer>();

            // Populating set
            as.add(1);
            as.add(2);
            as.add(3);
            as.add(4);
            as.add(5);

            System.out.println("AbstractSet before "
            + "removeAll() operation: "
            + as);

            // Creating another object of ArrayList<Integer>
            Collection<Integer> l = new ArrayList<Integer>();
            l.add(1);
            l.add(2);
            l.add(3);

            System.out.println("Collection Elements"
            + " to be removed: "
            + l);

            // Removing elements from AbstractSet
            // specified in list
            // using removeAll() method
            as.removeAll(l);

            // print arrlist1
            System.out.println("AbstractSet after "
            + "removeAll() operation: "
            + as);
        }

        catch (NullPointerException e) 
        {
            System.out.println("Exception thrown: " + e);
        }
    }
}

Output
AbstractSet before removeAll() operation: [1, 2, 3, 4, 5]
Collection Elements to be removed: [1, 2, 3]
AbstractSet after removeAll() operation: [4, 5]

Syntax

boolean removeAll(Collection<?> c);

  • Parameters: This method takes collection c as a parameter containing elements to be removed from this set.
  • Returns Value: This method returns true if this set changes as a result of the call.

Exceptions: 

  • UnsupportedOperationException: This is thrown if the operation is not supported by this set.
  • ClassCastException: This is thrown when the class of an element of this set is not compatible with the specified collection.
  • NullPointerException: Thrown when this set has a null element but the collection doesn’t allow nulls, or if the collection is null.

Example 2: This program shows how to use removeAll() Method on AbstractSet with Integer Values and handling NullPointerException.

Java 
// Java program to demonstrate 
// removeAll() method for Integer value 
import java.util.*; 

public class Geeks
 { 
	public static void main(String[] args) throws Exception 
	{ 
		try { 

			// Creating object of AbstractSet<Integer> 
			AbstractSet<Integer> 
			as = new TreeSet<Integer>(); 

			as.add(1); 
			as.add(2); 
			as.add(3); 
			as.add(4); 
			as.add(5); 

			System.out.println("AbstractSet before "
			+ "removeAll() operation: "
			+ as); 

			// Creating another object of ArrayList<Integer> 
			Collection<Integer> 
			l = new ArrayList<Integer>(); 
			l = null; 

			System.out.println("Collection Elements"
			+ " to be removed: "
			+ l); 

			// Removing elements from AbstractSet 
			// specified in list 
			// using removeAll() method 
			as.removeAll(l); 

			System.out.println("AbstractSet after "
			+ "removeAll() operation: "
			+ as); 
		} 

		catch (NullPointerException e) { 
			System.out.println("Exception thrown:" + e); 
		} 
	} 
}

Output
AbstractSet before removeAll() operation: [1, 2, 3, 4, 5]
Collection Elements to be removed: null
Exception thrown:java.lang.NullPointerException

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