The addAll(Collection collection) of java.util.Collection interface is used to add the Collection ‘collection’ to this existing collection. This method returns a boolean value depicting the successfulness of the operation. If the collection was added, it returns true, else it returns false.
Syntax:
Collection.addAll(Collection<E> collection)
Parameters: This method accepts a mandatory parameter collection of type Collection which is to be added to this collection.
Return Value: This method returns a boolean value depicting the successfulness of the operation. If the collection was added, it returns true, else it returns false.
Exceptions: This method throws following exceptions:
- UnsupportedOperationException: if the add operation is not supported by this collection
- ClassCastException: if the class of the specified element prevents it from being added to this collection
- NullPointerException: if the specified element is null and this collection does not permit null elements
- IllegalArgumentException: if some property of the element prevents it from being added to this collection
- IllegalStateException: if the element cannot be added at this time due to insertion restrictions
Below examples illustrate the Collection addAll() method:
Example 1: Using LinkedList Class
// Java code to illustrate boolean addAll() import java.util.*;import java.util.*; public class LinkedListDemo { public static void main(String args[]) { // Creating an empty LinkedList Collection<String> list = new LinkedList<String>(); // A collection is created Collection<String> collect = new LinkedList<String>(); collect.add("A"); collect.add("Computer"); collect.add("Portal"); collect.add("for"); collect.add("Geeks"); // Displaying the list System.out.println("The LinkedList is: " + list); // Appending the collection to the list list.addAll(collect); // displaying the modified LinkedList System.out.println("The new linked list is: " + list); }} |
The LinkedList is: [] The new linked list is: [A, Computer, Portal, for, Geeks]
Example 2: Using ArrayDeque Class
// Java code to illustrate addAll() method import java.util.*; public class ArrayDequeDemo { public static void main(String args[]) { // Creating an empty ArrayDeque Collection<String> de_que = new ArrayDeque<String>(); // Creating a new ArrayDeque Collection<String> deque = new ArrayDeque<String>(); deque.add("Welcome"); deque.add("To"); deque.add("Geeks"); deque.add("4"); deque.add("Geeks"); // Displaying the list System.out.println("The ArrayDeque is: " + de_que); // Appending the collection to the list de_que.addAll(deque); // displaying the modified ArrayDeque System.out.println("The new ArrayDeque is: " + de_que); }} |
The ArrayDeque is: [] The new ArrayDeque is: [Welcome, To, Geeks, 4, Geeks]
Example 3: Using ArrayList Class
// Java code to illustrate boolean addAll() import java.util.*; public class LinkedListDemo { public static void main(String args[]) { // Creating an empty ArrayList Collection<String> list = new ArrayList<String>(); // A collection is created Collection<String> collect = new ArrayList<String>(); collect.add("A"); collect.add("Computer"); collect.add("Portal"); collect.add("for"); collect.add("Geeks"); // Displaying the list System.out.println("The ArrayList is: " + list); // Appending the collection to the list list.addAll(collect); // displaying the modified ArrayList System.out.println("The new ArrayList is: " + list); }} |
The ArrayList is: [] The new ArrayList is: [A, Computer, Portal, for, Geeks]
Example 4: To demonstrate NullPointer Exception
// Java code to illustrate boolean addAll() import java.util.*; public class LinkedListDemo { public static void main(String args[]) { // Creating an empty ArrayList Collection<String> list = new ArrayList<String>(); // A collection is created Collection<String> collect = null; // Displaying the list System.out.println("The ArrayList is: " + list); try { // Appending the collection to the list list.addAll(collect); } catch (Exception e) { System.out.println("Exception: " + e); } }} |
The ArrayList is: [] Exception: java.lang.NullPointerException
Reference: https://docs.oracle.com/javase/9/docs/api/java/util/Collection.html#addAll-java.util.Collection-
