PriorityQueue containsAll(Collection) in Java

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

Syntax:

boolean java.util.AbstractCollection.containsAll(Collection<?> c)

This method takes one argument. This method returns true if this collection contains all of the elements in the specified collection.

Parameters: One parameter is required for this method.

c: collection to be checked for containment in this collection.

Returns: true if this collection contains all of the elements in the specified collection.

Throws:

1. ClassCastException - if the types of one or more elements in the specified collection are incompatible with this collection.

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

Approach 1: When no exception

Java

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

public class PriorityQueuecontainsAll {
    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> c = new PriorityQueue<Integer>();

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

        System.out.println(priorityQueue.containsAll(c));

    }
}

Output:

true

Approach 2: NullPointerException

Java

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

public class PriorityQueuecontainsAll {
    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> c = null;

        System.out.println(priorityQueue.containsAll(c));

    }
}

Output:

Exception in thread "main" java.lang.NullPointerException: Cannot invoke "java.util.Collection.iterator()" because "c" is null
	at java.base/java.util.AbstractCollection.containsAll(AbstractCollection.java:308)