AbstractCollection removeAll() method in Java with Example

Last Updated : 24 Dec, 2018

The Java.util.AbstractCollection.removeAll(Collection col) method is used to remove all the elements from the AbstractCollection, present in the collection specified.

Syntax:

AbstractCollection.removeAll(Collection col)

Parameters: This method accepts a mandatory parameter col which is the collection whose elements are to be removed from the AbstractCollection.

Return Value: This method returns true if the AbstractCollection is altered due to the operation at all, else False.

Exception: The method throws NullPointerException if the specified collection is null.

Below programs illustrate the Java.util.AbstractCollection.removeAll(Collection col) method:

Program 1:

// Java code to illustrate removeAll() 
import java.util.*; 
  
public class AbstractCollectionDemo { 
    public static void main(String args[]) 
    { 
  
        // Creating an empty AbstractCollection 
        AbstractCollection<String> collection 
            = new ArrayList<String>(); 
  
        // Use add() method to add 
        // elements in the AbstractCollection 
        collection.add("Geeks"); 
        collection.add("for"); 
        collection.add("Geeks"); 
        collection.add("10"); 
        collection.add("20"); 
  
        // Output the AbstractCollection 
        System.out.println("AbstractCollection: "
                           + collection); 
  
        // Creating an empty AbstractCollection 
        AbstractCollection<String> colcollection 
            = new ArrayList<String>(); 
  
        // Use add() method to add 
        // elements in the AbstractCollection 
        colcollection.add("Geeks"); 
        colcollection.add("for"); 
        colcollection.add("Geeks"); 
  
        // Remove the head using remove() 
        boolean changed 
            = collection.removeAll(colcollection); 
  
        // Print the result 
        if (changed) 
            System.out.println("Collection removed"); 
        else
            System.out.println("Collection not removed"); 
  
        // Print the final AbstractCollection 
        System.out.println("Final AbstractCollection: "
                           + collection); 
    } 
} 

Output:

AbstractCollection: [Geeks, for, Geeks, 10, 20]
Collection removed
Final AbstractCollection: [10, 20]

Program 2:

// Java code to illustrate removeAll() 
import java.util.*; 
  
public class AbstractCollectionDemo { 
    public static void main(String args[]) 
    { 
  
        // Creating an empty AbstractCollection 
        AbstractCollection<Integer> collection 
            = new ArrayList<Integer>(); 
  
        // Use add() method to 
        // add elements in the AbstractCollection 
        collection.add(1); 
        collection.add(2); 
        collection.add(3); 
        collection.add(10); 
        collection.add(20); 
  
        // Output the AbstractCollection 
        System.out.println("AbstractCollection: "
                           + collection); 
  
        // Creating an empty AbstractCollection 
        AbstractCollection<Integer> colcollection 
            = new ArrayList<Integer>(); 
  
        // Use add() method to add elements 
        // in the AbstractCollection 
        colcollection.add(30); 
        colcollection.add(40); 
        colcollection.add(50); 
  
        // Remove the head using remove() 
        boolean changed 
            = collection.removeAll(colcollection); 
  
        // Print the result 
        if (changed) 
            System.out.println("Collection removed"); 
        else
            System.out.println("Collection not removed"); 
  
        // Print the final AbstractCollection 
        System.out.println("Final AbstractCollection: "
                           + collection); 
    } 
} 

Output:

AbstractCollection: [1, 2, 3, 10, 20]
Collection not removed
Final AbstractCollection: [1, 2, 3, 10, 20]

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