Home » Core Java » threads » PriorityQueue example

About Ilias Tsagklis

Avatar photo
Ilias is a software developer turned online entrepreneur. He is co-founder and Executive Editor at Java Code Geeks.

PriorityQueue example

In this example we shall show you how to use a PriorityQueue. To use a PriorityQueue one should perform the following steps:

  • Create a new Comparator for Integer objects, that is a comparison function, which imposes a total ordering on some collection of objects.
  • Override the compare(Integer i, Integer j) method of Comparator in order to make a specified comparison.
  • Create a new PriorityQueue with a specified initial capacity, that orders its elements according to the specified comparator.
  • Use offer(Integer e) API method of PriorityQueue to insert an element to the PriorityQueue for comparison.
  • Use poll() API method of PriorityQueue to get the head of the queue,

as described in the code snippet below.  

package com.javacodegeeks.snippets.core;

import java.io.File;
import java.io.FileInputStream;
import java.io.IOException;
import java.util.Scanner;
import java.util.concurrent.ArrayBlockingQueue;
import java.util.concurrent.BlockingQueue;

import java.util.Comparator;
import java.util.PriorityQueue;
import java.util.Queue;

public class PriorityQueueExample {

    public static void main(String[] args) {


  PriorityQueue<Integer> pq =


    new PriorityQueue<Integer>(20,


    new Comparator<Integer>() {



@Override



  public int compare(Integer i, Integer j) {




int result = i % 2 - j % 2;




if (result == 0) {




    result = i - j;




}




return result;



  }


    });


  for (int i = 0; i < 20; i++) {


pq.offer(20 - i);

  }


  for (int i = 0; i < 20; i++) {


System.out.println(pq.poll());

  }
    }
}

Output:

2
4
6
8
10
12
14
16
18
20
1
3
5
7
9
11
13
15
17
19

  
This was an example of how to use a PriorityQueue in Java.

Do you want to know how to develop your skillset to become a Java Rockstar?

Subscribe to our newsletter to start Rocking right now!

To get you started we give you our best selling eBooks for FREE!

 

1. JPA Mini Book

2. JVM Troubleshooting Guide

3. JUnit Tutorial for Unit Testing

4. Java Annotations Tutorial

5. Java Interview Questions

6. Spring Interview Questions

7. Android UI Design

 

and many more ....

 

Receive Java & Developer job alerts in your Area

I have read and agree to the terms & conditions

 

Subscribe
Notify of
guest

This site uses Akismet to reduce spam. Learn how your comment data is processed.

0 Comments
Inline Feedbacks
View all comments