HashSet removeAll() method in Java with Example
The removeAll() method of java.util.HashSet 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:
Java
// 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 HashSet<Integer> HashSet<Integer> arrset1 = new HashSet<Integer>(); // Populating arrset1 arrset1.add( 1 ); arrset1.add( 2 ); arrset1.add( 3 ); arrset1.add( 4 ); arrset1.add( 5 ); // print arrset1 System.out.println("HashSet before " + "removeAll() operation : " + arrset1); // Creating another object of HashSet<Integer> HashSet<Integer> arrset2 = new HashSet<Integer>(); arrset2.add( 1 ); arrset2.add( 2 ); arrset2.add( 3 ); // print arrset2 System.out.println("Collection Elements" + " to be removed : " + arrset2); // Removing elements from arrset // specified in arrset2 // using removeAll() method arrset1.removeAll(arrset2); // print arrset1 System.out.println("HashSet after " + "removeAll() operation : " + arrset1); } catch (NullPointerException e) { System.out.println("Exception thrown : " + e); } } } |
Output:
HashSet before removeAll() operation : [1, 2, 3, 4, 5] Collection Elements to be removed : [1, 2, 3] HashSet after removeAll() operation : [4, 5]
Example 2: For NullPointerException
Java
// 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 HashSet<Integer> HashSet<Integer> arrset1 = new HashSet<Integer>(); // Populating arrset1 arrset1.add( 1 ); arrset1.add( 2 ); arrset1.add( 3 ); arrset1.add( 4 ); arrset1.add( 5 ); // print arrset1 System.out.println("HashSet before " + "removeAll() operation : " + arrset1); // Creating another object of HashSet<Integer> HashSet<Integer> arrset2 = null ; // print arrset2 System.out.println("Collection Elements" + " to be removed : " + arrset2); System.out.println("\nTrying to pass " + " null as a specified element\n"); // Removing elements from arrset // specified in arrset2 // using removeAll() method arrset1.removeAll(arrset2); // print arrset1 System.out.println("HashSet after " + "removeAll() operation : " + arrset1); } catch (NullPointerException e) { System.out.println("Exception thrown : " + e); } } } |
Output:
HashSet 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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