TreeSet removeAll() method in Java with Example

The removeAll() method of java.util.TreeSet 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: This method throws NullPointerException if this set contains a null element and the specified collection does not permit null elements (optional), or if the specified collection is null.

Below are the examples to illustrate the removeAll() method.

Example 1:

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// Java program to demonstrate
// removeAll() method for Integer value
  
import java.util.*;
  
public class GFG1 {
    public static void main(String[] argv) throws Exception
    {
  
        try {
  
            // Creating object of TreeSet<Integer>
            TreeSet<Integer>
                set1 = new TreeSet<Integer>();
  
            // Populating set1
            set1.add(1);
            set1.add(2);
            set1.add(3);
            set1.add(4);
            set1.add(5);
  
            // print set1
            System.out.println("TreeSet before "
                               + "removeAll() operation : "
                               + set1);
  
            // Creating another object of  TreeSet<Integer>
            TreeSet<Integer>
                set2 = new TreeSet<Integer>();
            set2.add(1);
            set2.add(2);
            set2.add(3);
  
            // print set2
            System.out.println("Collection Elements"
                               + " to be removed : "
                               + set2);
  
            // Removing elemnts from set
            // specified in set2
            // using removeAll() method
            set1.removeAll(set2);
  
            // print set1
            System.out.println("TreeSet after "
                               + "removeAll() operation : "
                               + set1);
        }
  
        catch (NullPointerException e) {
            System.out.println("Exception thrown : " + e);
        }
    }
}

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Output:

TreeSet before removeAll() operation : [1, 2, 3, 4, 5]
Collection Elements to be removed : [1, 2, 3]
TreeSet after removeAll() operation : [4, 5]

Example 2: For NullPointerException

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// Java program to demonstrate
// removeAll() method for Integer value
  
import java.util.*;
  
public class GFG1 {
    public static void main(String[] argv) throws Exception
    {
  
        try {
  
            // Creating object of TreeSet<Integer>
            TreeSet<Integer>
                set1 = new TreeSet<Integer>();
  
            // Populating set1
            set1.add(1);
            set1.add(2);
            set1.add(3);
            set1.add(4);
            set1.add(5);
  
            // print set1
            System.out.println("TreeSet before "
                               + "removeAll() operation : "
                               + set1);
  
            // Creating another object of  TreeSet<Integer>
            TreeSet<Integer>
                set2 = null;
  
            // print set2
            System.out.println("Collection Elements"
                               + " to be removed : "
                               + set2);
  
            System.out.println("\nTrying to pass "
                               + "null as a specified element\n");
  
            // Removing elemnts from set
            // specified in set2
            // using removeAll() method
            set1.removeAll(set2);
  
            // print set1
            System.out.println("TreeSet after "
                               + "removeAll() operation : "
                               + set1);
        }
  
        catch (NullPointerException e) {
            System.out.println("Exception thrown : " + e);
        }
    }
}

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Output:

TreeSet before removeAll() operation : [1, 2, 3, 4, 5]
Collection Elements to be removed : null

Trying to pass null as a specified element

Exception thrown : java.lang.NullPointerException


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