Urgent java problems

Question

Ok here's my situation... I'm having to catch up in my software development class at university, missed a few lessons so now I'm finding it incredibly difficult.
I'm working through a bluej book 'Objects First with Java' and as much as I'd like to sit and work each question out, it is taking me far too long and I'm not gonna manage so this will probably be the first post of many.
So here's where I am
(pg. 110, ex. 4.28)
It's a simple auction program that lets you create a bidder, a lot(something to bid on), an auction and of course the ability to bid.
What I'm being asked...
Add a close method to the Auction class. This should iterate over the collection of lots and print out details of all the lots. You can use either a for-each loop or a while loop. Any lot that has had at least one bid for it is considered to be sold. For lots that have been sold, the details should include the name of the successful bidder, and the value of the winning bid. For lots that have not been sold, print a message that indicates this fact.
import java.util.ArrayList;
import java.util.Iterator;
* A simple model of an auction.
* The auction maintains a list of lots of arbitrary length.
* @author David J. Barnes and Michael Kolling.
* @version 2008.03.30
public class Auction
    // The list of Lots in this auction.
    private ArrayList<Lot> lots;
    // The number that will be given to the next lot entered
    // into this auction.
    private int nextLotNumber;
     * Create a new auction.
    public Auction()
        lots = new ArrayList<Lot>();
        nextLotNumber = 1;
     * Enter a new lot into the auction.
     * @param description A description of the lot.
    public void enterLot(String description)
        lots.add(new Lot(nextLotNumber, description));
        nextLotNumber++;
     * Show the full list of lots in this auction.
    public void showLots()
        for(Lot lot : lots) {
            System.out.println(lot.toString());
     * Bid for a lot.
     * A message indicating whether the bid is successful or not
     * is printed.
     * @param number The lot number being bid for.
     * @param bidder The person bidding for the lot.
     * @param value  The value of the bid.
    public void bidFor(int lotNumber, Person bidder, long value)
        Lot selectedLot = getLot(lotNumber);
        if(selectedLot != null) {
            boolean successful = selectedLot.bidFor(new Bid(bidder, value));
            if(successful) {
                System.out.println("The bid for lot number " +
                                   lotNumber + " was successful.");
            else {
                // Report which bid is higher.
                Bid highestBid = selectedLot.getHighestBid();
                System.out.println("Lot number: " + lotNumber +
                                   " already has a bid of: " +
                                   highestBid.getValue());
     * Return the lot with the given number. Return null
     * if a lot with this number does not exist.
     * @param lotNumber The number of the lot to return.
    public Lot getLot(int lotNumber)
        if((lotNumber >= 1) && (lotNumber < nextLotNumber)) {
            // The number seems to be reasonable.
            Lot selectedLot = lots.get(lotNumber - 1);
            // Include a confidence check to be sure we have the
            // right lot.
            if(selectedLot.getNumber() != lotNumber) {
                System.out.println("Internal error: Lot number " +
                                   selectedLot.getNumber() +
                                   " was returned instead of " +
                                   lotNumber);
                // Don't return an invalid lot.
                selectedLot = null;
            return selectedLot;
        else {
            System.out.println("Lot number: " + lotNumber +
                               " does not exist.");
            return null;
    public void close(){
        Iterator<Lot> it = lots.iterator();
        for(Lot lot : lots){
        if(lots.contains(null)){
            System.out.println(lot.toString() + " has not been sold.");
}I know my 'close' method is a bit shoddy and doesn't utilise the iterator yet but I tested it and it compiled ok but nothing happened :/
Is the for-each loop a wise move? Ideas would be greatly appreciated! I tried a while loop first but wasn't really getting anywhere. One of my many problems in this is that I don't really understand where the methods I'm calling from are coming from either, I really don't have a good base understanding of the language :( for instance lots.toString() where does the .toString come from, thats an arraylist method then yeah?
I am feeling that the book is going pretty fast, some questions are fairly simple then suddenly I feel like it's never even taught me enough to even work a question out on my own - obviously just starting out at programming though so it may be completely obvious but if you don't know it you don't know it :/
Anyway folks I hope you can help as, like I said, it's pretty important to me and I don't know how the forum works but if I'm the one that will have the power to award the points for an answer then I will deal them out appropriately.
Cheers
Edited by: jpjenkins on Nov 14, 2008 2:00 AM

Answer 1

jpjenkins wrote:
Wow what a nice introduction to the forum.
My time management skills are good, thanks for the advice though. We must have a different notion of what the word "good" means...
But how can I be 'all high an mighty' It sounded like you were doing us a favor by handing out some forum/duke points/stars while you are the one looking for help.
when I said I don't know how the forum works, sounds like you've got a complex man, was just trying to let peeps know I was going to be fair.Wow, your assessment of my psychic state is impressive! By studying your two posts here, I conclude you're a lazy twit.
I do apologise however, I wrote this after 3 hours of studying and my stress must have transferred into the post.Then study some more!
To the point: "I tested it and it compiled ok but nothing happened :/ " - I just wanted to know where I had gone wrong in the close method as I expected it to print out a lot that doesn't have a bid on it.
I have worked through the book at a steady pace, I simply don't have the luxury to sit and work out where I had gone wrong in each question, sorry if I misled you into thinking I expected you to do it for me, these aren't necessary questions for me to do, they're just giving me a good grounding for my project which has to be handed in on the 5th of December. Trying to speed my workrate up by getting advice on my shoddy code.
Hope someone can helpI still don't see a specific question.