PriorityQueue addAll(Collection) in Java

addAll(Collection): This method is available in java.util.PriorityQueue class of Java.

Syntax:

boolean java.util.AbstractQueue.addAll(Collection<? extends K> c)

This method takes one argument. This method adds all of the elements in the specified collection to this queue.

Parameters: One parameter is required for this method.

c: a collection containing elements to be added to this queue.

Returns: true if this queue changed as a result of the call.

Throws:

1. ClassCastException - if the class of an element of the specified collection prevents it from being added to this queue.

2. NullPointerException - if the specified collection contains a null element and this queue does not permit null elements, or if the specified collection is null.

3. IllegalArgumentException - if some property of an element of the specified collection prevents it from being added to this queue, or if the specified collection is this queue.

4. IllegalStateException - if not all the elements can be added at this time due to insertion restrictions.

Approach 1: When no exception

Java

import java.util.Collection;
import java.util.PriorityQueue;

public class PriorityQueueaddAll {
    public static void main(String[] args) {

        PriorityQueue<Integer> priorityQueue = 
                 new PriorityQueue<Integer>();

        priorityQueue.add(12);
        priorityQueue.add(5);
        priorityQueue.add(10);
        priorityQueue.add(2);

        Collection<Integer> collection = 
                new PriorityQueue<Integer>();

        collection.add(19);
        collection.add(3);

        System.out.println(priorityQueue.addAll(collection));

    }
}

Output:

true

Approach 2: NullPointerException 

Java

import java.util.Collection;
import java.util.PriorityQueue;

public class PriorityQueueaddAll {
    public static void main(String[] args) {

        PriorityQueue<Integer> priorityQueue = 
             new PriorityQueue<Integer>();

        priorityQueue.add(12);
        priorityQueue.add(5);
        priorityQueue.add(10);
        priorityQueue.add(2);

        Collection<Integer> collection = null;
        System.out.println(priorityQueue.addAll(collection));

    }
}

Output:

Exception in thread "main" java.lang.NullPointerException
	at java.base/java.util.AbstractQueue.addAll(AbstractQueue.java:182)