1. 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:

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   // 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]);     } }

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   Output:

   
   

   
   

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

   Program 2:

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   // 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]);     } }

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   Output:

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

2. 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: The method might throw two types of 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.

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   // 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]);     } }

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   Output:

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

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