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AbstractSet removeAll() Method in Java with Examples

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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


Last Updated : 30 Sep, 2019
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