// Java program to demonstrate working of priority queue in Java 
import java.util.*; 

class Example 
{ 
	public static void main(String args[]) 
	{ 
		// Creating empty priority queue 
		PriorityQueue<String> pQueue = 
						new PriorityQueue<String>(); 

		// Adding items to the pQueue using add() 
		pQueue.add("C"); 
		pQueue.add("C++"); 
		pQueue.add("Java"); 
		pQueue.add("Python"); 

		// Printing the most priority element 
		System.out.println("Head value using peek function:"
										+ pQueue.peek()); 

		// Printing all elements 
		System.out.println("The queue elements:"); 
		Iterator itr = pQueue.iterator(); 
		while (itr.hasNext()) 
			System.out.println(itr.next()); 

		// Removing the top priority element (or head) and 
		// printing the modified pQueue using poll() 
		pQueue.poll(); 
		System.out.println("After removing an element" + 
						"with poll function:"); 
		Iterator<String> itr2 = pQueue.iterator(); 
		while (itr2.hasNext()) 
			System.out.println(itr2.next()); 

		// Removing Java using remove() 
		pQueue.remove("Java"); 
		System.out.println("after removing Java with" + 
						" remove function:"); 
		Iterator<String> itr3 = pQueue.iterator(); 
		while (itr3.hasNext()) 
			System.out.println(itr3.next()); 

		// Check if an element is present using contains() 
		boolean b = pQueue.contains("C"); 
		System.out.println ( "Priority queue contains C " + 
							"or not?: " + b); 

		// Getting objects from the queue using toArray() 
		// in an array and print the array 
		Object[] arr = pQueue.toArray(); 
		System.out.println ( "Value in array: "); 
		for (int i = 0; i<arr.length; i++) 
		System.out.println ( "Value: " + arr[i].toString()) ; 
	} 
}