AbstractSet removeAll() Method in Java (original) (raw)

Last Updated : 12 Feb, 2025

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 AbstractSet as = new TreeSet();

        // 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