The removeAll() method of Java AbstractSet class is used to remove from this set all of its elements that are contained in the specified collection.
Syntax:
public 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 changed as a result of the call.
Exception: The method throws three types of exception:
- 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 – This is thrown when this set contains a null element and the specified collection does not permit null elements, or if the collection is null.
Below are the examples to illustrate the removeAll() method.
Program 1:
// Java program to demonstrate// removeAll() method for Integer value  import java.util.*;  public class GFG1 {    public static void main(String[] args) throws Exception    {          try {              // Creating object of AbstractSet<Integer>            AbstractSet<Integer>                abs_set = new TreeSet<Integer>();              // Populating abs_set            abs_set.add(1);            abs_set.add(2);            abs_set.add(3);            abs_set.add(4);            abs_set.add(5);              // print abs_set            System.out.println("AbstractSet before "                               + "removeAll() operation : "                               + abs_set);              // Creating another object of ArrayList<Integer>            Collection<Integer>                arrlist2 = new ArrayList<Integer>();            arrlist2.add(1);            arrlist2.add(2);            arrlist2.add(3);              // print arrlist2            System.out.println("Collection Elements"                               + " to be removed : "                               + arrlist2);              // Removing elements from AbstractSet            // specified in arrlist2            // using removeAll() method            abs_set.removeAll(arrlist2);              // print arrlist1            System.out.println("AbstractSet after "                               + "removeAll() operation : "                               + abs_set);        }          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]
Example 2: For NullPointerException
// Java program to demonstrate// removeAll() method for Integer value  import java.util.*;  public class GFG1 {    public static void main(String[] args) throws Exception    {          try {              // Creating object of AbstractSet<Integer>            AbstractSet<Integer>                abs_set = new TreeSet<Integer>();              // Populating abs_set            abs_set.add(1);            abs_set.add(2);            abs_set.add(3);            abs_set.add(4);            abs_set.add(5);              // print abs_set            System.out.println("AbstractSet before "                               + "removeAll() operation : "                               + abs_set);              // Creating another object of ArrayList<Integer>            Collection<Integer>                arrlist2 = new ArrayList<Integer>();            arrlist2 = null;              // print arrlist2            System.out.println("Collection Elements"                               + " to be removed : "                               + arrlist2);              // Removing elements from AbstractSet            // specified in arrlist2            // using removeAll() method            abs_set.removeAll(arrlist2);              // print arrlist1            System.out.println("AbstractSet after "                               + "removeAll() operation : "                               + abs_set);        }          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
