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Java PriorityQueue toArray() Method with Example

PriorityQueue Class toArray() method: Here, we are going to learn about the toArray() method of PriorityQueue Class with its syntax and example.
Submitted by Preeti Jain, on March 11, 2020

PriorityQueue Class toArray() method

Syntax:

    public Object[] toArray();
    public Type[] toArray(Type[] ty);

• toArray() method is available in java.util package.
• toArray() method is used to return an object array (Object []) that holds all of the objects in this PriorityQueue.
• toArray(Type[] ty) method is used to return the same array as the parameter type that holds all of the objects in this PriorityQueue.
• These methods may throw an exception at the time of returning an array.
  NullPointerException: This exception may throw when the given parameter is null exists.
• These are non-static methods and it is accessible with the class object and if we try to access these methods with the class name then also we will get an error.

Parameter(s):

• In the first case, toArray(), It does not accept any parameter.
• In the first case, toArray(Type[] ty), Type[] ty – represents the array into which the sorted objects of the queue.

Return value:

In the first cases, the return type of the method is Object [], – it returns an object array with full of elements in this PriorityQueue.

In the second cases, the return type of the method is Type [], – it returns the same array as the parameter type array.

Example:

// Java program to demonstrate the example 
// of toArray() method of PriorityQueue

import java.util.*;

public class ToArrayOfPriorityQueue {
    public static void main(String args[]) {
        // Instantiate PriorityQueue
        PriorityQueue < String > pq = new PriorityQueue < String > (10);
        String[] s_arr1 = new String[5];

        // By using add() method is add
        // the given element into priority
        // queue
        pq.add("C");
        pq.add("C++");
        pq.add("JAVA");
        pq.add("PHP");
        pq.add("ANDROID");

        // Display PriorityQueue
        System.out.println("PriorityQueue: " + pq);

        // By using toArray() method is to
        // convert the given object to
        // an object array
        Object[] o_arr = pq.toArray();

        System.out.println("pq.toArray(): ");
        for (int i = 0; i < o_arr.length; ++i)
            System.out.println(o_arr[i].toString());

        System.out.println();

        // By using toArray(arr) method is to
        // contains all of the priority queue
        // elements

        String[] s_arr2 = pq.toArray(s_arr1);
        System.out.println("pq.toArray(s_arr1): ");

        for (int i = 0; i < s_arr2.length; ++i)
            System.out.println(s_arr2[i]);
    }
}

Output

PriorityQueue: [ANDROID, C, JAVA, PHP, C++]
pq.toArray(): 
ANDROID
C
JAVA
PHP
C++

pq.toArray(s_arr1): 
ANDROID
C
JAVA
PHP
C++