The addAll() method of CopyonWriteArraySet method adds all the element of the specified collection to this CopyOnWriteArraySet which are not present in it. This methods results the union of the two collections.
Syntax:
public boolean addAll(Collection<E> c)
Parameters: This method accepts a parameter c which is the collection containing elements to be added to this set.
Return Value: This method returns a boolean value such as true, if the CopyOnWriteArraySet is changed. Else this method returns false.
Exceptions: This method throws NullPointerException if the specified collection is null.
Below program illustrates the addAll() function of CopyOnWriteArrayList class:
Program 1: In the below program, the specified collection elements are added to the CopyOnWriteArraySet. Since 50 is common in both the collections, it is added single time.
// Java Program to illustrate the// CopyOnWriteArraySet addall() method in Java  import java.util.concurrent.CopyOnWriteArraySet;import java.util.*;  public class GFG {    public static void main(String[] args)    {          // create object of CopyOnWriteArraySet        CopyOnWriteArraySet<Integer> ArrSet            = new CopyOnWriteArraySet<Integer>();          // Add elements        ArrSet.add(10);        ArrSet.add(20);        ArrSet.add(30);        ArrSet.add(50);          // print CopyOnWriteArraySet        System.out.println("CopyOnWriteArraySet: "                           + ArrSet);          // create object of ArrayList        ArrayList<Integer> Arrlist            = new ArrayList<Integer>();          // Add elements        Arrlist.add(50);        Arrlist.add(60);        Arrlist.add(70);        Arrlist.add(80);          // print ArrayList        System.out.println("ArrayList: "                           + Arrlist);          // adding all elements of Arraylist        // in the CopyOnWriteArraySet        ArrSet.addAll(Arrlist);          // print updated CopyOnWriteArraySet        System.out.println("Updated CopyOnWriteArraySet: "                           + ArrSet);    }} |
CopyOnWriteArraySet: [10, 20, 30, 50] ArrayList: [50, 60, 70, 80] Updated CopyOnWriteArraySet: [10, 20, 30, 50, 60, 70, 80]
Program 2: To show NullpointerException
// Java Program to illustrate the// CopyOnWriteArraySet addall() method in Java  import java.util.concurrent.CopyOnWriteArraySet;import java.util.*;  public class GFG {    public static void main(String[] args)    {          // create object of CopyOnWriteArraySet        CopyOnWriteArraySet<Integer> ArrSet            = new CopyOnWriteArraySet<Integer>();          // Add elements        ArrSet.add(10);        ArrSet.add(20);        ArrSet.add(30);        ArrSet.add(50);          // print CopyOnWriteArraySet        System.out.println("CopyOnWriteArraySet: "                           + ArrSet);          // create object of ArrayList        ArrayList<Integer> Arrlist            = new ArrayList<Integer>();          try {              // adding null to the CopyOnWriteArraySet            // This will throw NullPointerException            ArrSet.addAll(null);        }        catch (Exception e) {            System.out.println(e);        }    }} |
CopyOnWriteArraySet: [10, 20, 30, 50] java.lang.NullPointerException
