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]
