Java Collection addAll() method

The addAll() method of Java Collection Interface appends or inserts all the elements of the specified collection to this collection.

Syntax

Parameters

The parameter 'c' represents the elements to be added into this Collection.

Return Value

The addAll() method returns a Boolean value true, if the queue has changed as a result of this call else it returns false.

Throws

The addAll() method throws:

UnsupportedOperationException - if the addAll 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 or the specified collection is null and this collection does not allow null elements

IllegalArgumentException- if some property of the element prevents it from being added to this collection

IllegalStateException- if all the elements cannot be inserted at this time due to some insertion restrictions

Example 1

import java.util.ArrayList;
import java.util.HashSet;
import java.util.List;
import java.util.Set;
public class JavaCollectionAddAllExample1 {
    public static void main(String[] args) {
        Set<Integer> set = new HashSet<>();
        List<Integer> list = new ArrayList<Integer>();
        System.out.println("Before applying addAll() : " );
        System.out.println("Elements in queue : "+ set);
        for (int i = 1; i < 11; i++) {
            int j = i *5;
            //
            list.add(j);
        }
        System.out.println("Elements in list : "+list);
        System.out.println();
        System.out.println("After applying addAll : ");
        //will add all the elements in the set which are present in list
        set.addAll(list);
        System.out.println("Elements in queue : " + set);
        System.out.println("Elements in list : "+list);
    }
}

Test it Now

Output:

Before applying addAll() : 
Elements in queue : []
Elements in list : [5, 10, 15, 20, 25, 30, 35, 40, 45, 50]

After applying addAll : 
Elements in queue : [50, 35, 20, 5, 40, 25, 10, 45, 30, 15]
Elements in list : [5, 10, 15, 20, 25, 30, 35, 40, 45, 50]

Example 2

import java.util.concurrent.ConcurrentLinkedQueue;
public class JavaCollectionAddAllExample2 {
    public static void main(String[] args) {
        ConcurrentLinkedQueue<Integer> queue = new ConcurrentLinkedQueue<Integer>();
        for (int i=0;i<=5;i++){
            queue.add(i);
        }
        //will pass an error because both the collection can not be same
        queue.addAll(queue);
        System.out.println(queue);
    }
}

Test it Now

Output:

Exception in thread "main" java.lang.IllegalArgumentException
	at java.util.concurrent.ConcurrentLinkedQueue.addAll(ConcurrentLinkedQueue.java:526)
	at com.javaTpoint.JavaCollectionAddAllExample2.main(JavaCollectionAddAllExample2.java:11)

Example 3

import java.util.ArrayDeque;
import java.util.Deque;
import java.util.concurrent.ConcurrentLinkedQueue;
public class JavaCollectionAddAllExample3 {
    public static void main(String[] args) {
        ConcurrentLinkedQueue<Integer> queue = new ConcurrentLinkedQueue<Integer>();
        Deque<Integer> deque=new ArrayDeque<>();
        for (int i=0;i<=5;i++){
            queue.add(i);
        }
        //will give an error for null elements
        deque.add(null);
        queue.addAll(deque);
        System.out.println(queue);
    }
}

Test it Now

Output:

Exception in thread "main" java.lang.NullPointerException
	at java.util.ArrayDeque.addLast(ArrayDeque.java:249)
	at java.util.ArrayDeque.add(ArrayDeque.java:423)
	at com.javaTpoint.JavaCollectionAddAllExample3.main(JavaCollectionAddAllExample3.java:13)

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