RetroSearch Browse

Home - News ( United States | United Kingdom | Italy | Germany ) - Football scores

Showing content from https://www.geeksforgeeks.org/java/copyonwritearrayset-retainall-method-in-java-with-example/ below:

CopyOnWriteArraySet retainAll() method in Java with Example

Last Updated : 24 Dec, 2018

The

retainAll()

method of

java.util.concurrent.CopyOnWriteArraySet

class is used to retain from this set all of its elements that are contained in the specified collection.

Syntax:

public boolean retainAll(Collection c)

Parameters:

This method takes

collection c

as a parameter containing elements to be retained 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

retainAll()

method.

Example 1: Java


 // Java program to demonstrate
// retainAll() method for Integer value

import java.util.concurrent.*;

public class GFG1 {
    public static void main(String[] argv) throws Exception
    {

        try {

            // Creating object of CopyOnWriteArraySet<Integer>
            CopyOnWriteArraySet<Integer>
                set1 = new CopyOnWriteArraySet<Integer>();

            // Populating set1
            set1.add(1);
            set1.add(2);
            set1.add(3);
            set1.add(4);
            set1.add(5);

            // print set1
            System.out.println("CopyOnWriteArraySet before "
                               + "retainAll() operation : "
                               + set1);

            // Creating another object of  CopyOnWriteArraySet<Integer>
            CopyOnWriteArraySet<Integer>
                set2 = new CopyOnWriteArraySet<Integer>();
            set2.add(1);
            set2.add(2);
            set2.add(3);

            // print set2
            System.out.println("Collection Elements"
                               + " to be retained : "
                               + set2);

            // Removing elements from set
            // specified in set2
            // using retainAll() method
            set1.retainAll(set2);

            // print set1
            System.out.println("CopyOnWriteArraySet after "
                               + "retainAll() operation : "
                               + set1);
        }

        catch (NullPointerException e) {
            System.out.println("Exception thrown : " + e);
        }
    }
}

Output:

CopyOnWriteArraySet before retainAll() operation : [1, 2, 3, 4, 5]
Collection Elements to be retained : [1, 2, 3]
CopyOnWriteArraySet after retainAll() operation : [1, 2, 3]

Example 2:

For

NullPointerException Java


 // Java program to demonstrate
// retainAll() method for Integer value

import java.util.concurrent.*;

public class GFG1 {
    public static void main(String[] argv) throws Exception
    {

        try {

            // Creating object of CopyOnWriteArraySet<Integer>
            CopyOnWriteArraySet<Integer>
                set1 = new CopyOnWriteArraySet<Integer>();

            // Populating set1
            set1.add(1);
            set1.add(2);
            set1.add(3);
            set1.add(4);
            set1.add(5);

            // print set1
            System.out.println("CopyOnWriteArraySet before "
                               + "retainAll() operation : "
                               + set1);

            // Creating another object of  CopyOnWriteArraySet<Integer>
            CopyOnWriteArraySet<Integer>
                set2 = null;

            // print set2
            System.out.println("Collection Elements"
                               + " to be retained : "
                               + set2);

            System.out.println("\nTrying to pass "
                               + "null as a specified element\n");

            // Removing elements from set
            // specified in set2
            // using retainAll() method
            set1.retainAll(set2);

            // print set1
            System.out.println("CopyOnWriteArraySet after "
                               + "retainAll() operation : "
                               + set1);
        }

        catch (NullPointerException e) {
            System.out.println("Exception thrown : " + e);
        }
    }
}

Output:

CopyOnWriteArraySet before retainAll() operation : [1, 2, 3, 4, 5]
Collection Elements to be retained : null

Trying to pass null as a specified element

Exception thrown : java.lang.NullPointerException

RetroSearch is an open source project built by @garambo | Open a GitHub Issue

Search and Browse the WWW like it's 1997 | Search results from DuckDuckGo

HTML: 3.2 | Encoding: UTF-8 | Version: 0.7.4