PriorityQueue toArray() Method in Java

Last Updated : 10 Dec, 2018

The java.util.PriorityQueue.toArray() method in Java is used to form an array of the same elements as that of the Priority Queue. Basically, it copies all the element from a priority queue to a new array.

Syntax:

Object[] arr = Priority_Queue.toArray()

Parameters: The method does not take any parameters.

Return Value: The method returns an array containing the elements similar to the priority queue.

Below programs illustrate the java.util.PriorityQueue.toArray() method.
Program 1:

   // Java code to illustrate toArray() 
import java.util.*; 
  
public class PriorityQueueDemo { 
    public static void main(String args[]) 
    { 
        // Creating an empty PriorityQueue 
        PriorityQueue<String> queue = new PriorityQueue<String>(); 
  
        // Use add() method to add elements into the Queue 
        queue.add("Welcome"); 
        queue.add("To"); 
        queue.add("Geeks"); 
        queue.add("For"); 
        queue.add("Geeks"); 
  
        // Displaying the PriorityQueue 
        System.out.println("The PriorityQueue: " + queue); 
  
        // Creating the array and using toArray() 
        Object[] arr = queue.toArray(); 
  
        System.out.println("The array is:"); 
        for (int j = 0; j < arr.length; j++) 
            System.out.println(arr[j]); 
    } 
} 
 
  

Output:

  The PriorityQueue: [For, Geeks, To, Welcome, Geeks]  The array is:  For  Geeks  To  Welcome  Geeks

Program 2:

   // Java code to illustrate toArray() 
import java.util.*; 
  
public class PriorityQueueDemo { 
    public static void main(String args[]) 
    { 
        // Creating an empty PriorityQueue 
        PriorityQueue<Integer> queue = new PriorityQueue<Integer>(); 
  
        // Use add() method to add elements into the Queue 
        queue.add(10); 
        queue.add(15); 
        queue.add(30); 
        queue.add(20); 
        queue.add(5); 
        queue.add(25); 
  
        // Displaying the PriorityQueue 
        System.out.println("The PriorityQueue: " + queue); 
  
        // Creating the array and using toArray() 
        Object[] arr = queue.toArray(); 
  
        System.out.println("The array is:"); 
        for (int j = 0; j < arr.length; j++) 
            System.out.println(arr[j]); 
    } 
} 
 
  

Output:

  The PriorityQueue: [5, 10, 25, 20, 15, 30]  The array is:  5  10  25  20  15  30

The java.util.PriorityQueue.toArray(arr[]) method in Java is used to form an array of the same elements as that of the Priority Queue. Basically, it copies all the element from a priority queue to a new array. It creates multiple arrays, unlike the previous method without parameters. This method copies all of the elements into the arr[].
Syntax:

Object[] arr1 = Priority_Queue.toArray(arr[])

Parameters: The method accepts one parameter arr[] into which all of the elements of the queue are to be copied.

Return Value: The method returns an array containing the elements similar to the priority queue.

Exception:

ArrayStoreException: When the mentioned array is of the different type and is not able to compare with the elements mentioned in the queue.
NullPointerException: If the array is Null, then this exception is thrown.

Below program illustrates the working of the java.util.PriorityQueue.toArray(arr[]) method.

   // Java code to illustrate toArray(arr[]) 
import java.util.*; 
  
public class PriorityQueueDemo { 
    public static void main(String args[]) 
    { 
        // Creating an empty PriorityQueue 
        PriorityQueue<String> queue = new PriorityQueue<String>(); 
  
        // Use add() method to add elements into the Queue 
        queue.add("Welcome"); 
        queue.add("To"); 
        queue.add("Geeks"); 
        queue.add("For"); 
        queue.add("Geeks"); 
  
        // Displaying the PriorityQueue 
        System.out.println("The PriorityQueue: " + queue); 
  
        // Creating the array and using toArray() 
        String[] arr = new String[5]; 
        String[] arr1 = queue.toArray(arr); 
          
        // Displaying arr 
        System.out.println("The arr[] is:"); 
        for (int j = 0; j < arr.length; j++) 
            System.out.println(arr[j]); 
          
        // Displaying arr1 
        System.out.println();     
        System.out.println("The arr1[] is:"); 
        for (int i = 0; i < arr1.length; i++) 
            System.out.println(arr1[i]); 
    } 
} 
 
  

Output:

  The PriorityQueue: [For, Geeks, To, Welcome, Geeks]  The arr[] is:  For  Geeks  To  Welcome  Geeks    The arr1[] is:  For  Geeks  To  Welcome  Geeks

AbstractQueue addAll() method in Java with examples

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