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Please ensure that: Your code is properly formatted as code block - see the sidebar (About on mobile) for instructions You include any and all error messages in full You ask clear questions You demonstrate effort in solving your question/problem - plain posting your assignments is forbidden (and such posts will be removed) as is asking for or giving solutions. Trying to solve problems on your own is a very important skill. Also, see Learn to help yourself in the sidebar If any of the above points is not met, your post can and will be removed without further warning. Code is to be formatted as code block (old reddit: empty line before the code, each code line indented by 4 spaces, new reddit: https://i.imgur.com/EJ7tqek.png ) or linked via an external code hoster, like pastebin.com, github gist, github, bitbucket, gitlab, etc. Please, do not use triple backticks (```) as they will only render properly on new reddit, not on old reddit. Code blocks look like this: public class HelloWorld { public static void main(String[] args) { System.out.println("Hello World!"); } } You do not need to repost unless your post has been removed by a moderator. Just use the edit function of reddit to make sure your post complies with the above. If your post has remained in violation of these rules for a prolonged period of time (at least an hour), a moderator may remove it at their discretion. In this case, they will comment with an explanation on why it has been removed, and you will be required to resubmit the entire post following the proper procedures. To potential helpers Please, do not help if any of the above points are not met, rather report the post. We are trying to improve the quality of posts here. In helping people who can't be bothered to comply with the above points, you are doing the community a disservice. I am a bot, and this action was performed automatically. Please contact the moderators of this subreddit if you have any questions or concerns. More on reddit.com

Offer is essentially the same thing as Add, it simply inserts it into the PQ. If you are wondering why the result that is printed is not in a sorted order as you might expect, read the top paragraph again: Priority Queues in Java are implemented using a Heap. Printing a Heap is different than printing an Array / ArrayList. If you implement your own PQ using an Array ( which, imo, is a good practice to try ), printing the Queue would look sorted. More on reddit.com

The first thing to understand is a comparison function. A comparison function takes two objects, let's call them x and y. if x is less than y, it returns a negative number. if x is greater than y, it returns a positive number. if x is equal to y, it returns zero. The meaning of the terms "less than", "greater than", and "equal" are up to you. For example, if you are comparing your Node objects, you probably want to consider a Node with the smaller distance value to be "less than" one with a greater distance. With that in mind, the easiest thing for you to do is going to make your Node class implement the Comparable interface. Then you won't have to anything complicated to create a PriorityQueue. The Comparable interface requires you to create a function compareTo, which behaves as I described above. In this function, this takes the role of x and the function's parameter takes the role of y. So something like: class Node implements Comparable { public int compareTo(Node other) { return this.distance - other.distance; } } Pay attention to what the result of that subtraction would be. If this.distance is smaller, then the result is a negative number. If this.distance is bigger, then the result is a positive number. And if the distance values are equal, the result is zero. So this behaves exactly like a comparison function as described above. More on reddit.com