Implementing Search Algorithm To Solve 8 Puzzle

I have been working on a program that takes in a 2d array (there is a method to convert to 1d as necessary) and uses it as an 8 puzzle, which the program then solves (if it is solvable) using the A* Search algorithm, outputting each solution move. It needs error checkers/traps/exception handlers, and be able to create an 8 puzzle from user input, create an 8 puzzle from file input, and create an 8 puzzle from file input and then output to another file the solution move sequence. I have gotten nearly everything done except for implement the algorithm itself and the methods for handling input from files or output to files (the input/output file methods are a minor problem that I can probably solve fairly easily, I just want to be able to test the a* with the puzzle created from user input first.

I have taken several cracks at it, but I am not really good with Java in this type of situation and this is hurting me a lot. I have put in a method to determine if a puzzle is solvable, but the A* algorithm still eludes me. I understand the concept of the algorithm, you have a heuristic function, a cost function (each move equals 1 in this case), and you add the two together to get f(n), choosing the move that will get you the closest to your goal (best first search basically). here is what I have so far that works:

import java.io.File;
import java.io.IOException;
import java.util.Queue;
import java.util.Scanner;
public class Puzzle {
public static void main(String[] args) throws IOException {

[Code] ....

I have it outputting things to make sure all that works already, I have all the error handlers, but I think that before I can even implement the A*search algorithm, there may be something else I need. Conceptually, I understand I need Nodes, States and Stacks, and Queues (I think, I am not sure about this), but with the way my code has been made so far, I am not sure how to implement those and then implement them with the A* algorithm. What I should do next? I have looked at the code of other uses of A* algorithm(that is how I found out I might need Java data structures like queue and stack and list), but I am not sure exactly where to go to from where I am.