Hi, I'm quite new at programming and I've been finding the external method calls quite hard to get right in completing this particular exercise...

Exercise 4.28
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 (Which I chose to use) 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.

The Auction code with my close method is:

Code:
import java.util.ArrayList;
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(){
        for (Lot lotLoopVariable : lots ){
            System.out.println(lotLoopVariable);
            if(){
                
            }
            
        }
    }
        
    
}
There is also a Person, Lot and Bid class...The person and bid classes are linked and the lot produces the highest bid...but I don't know how to get that information and display it in the close method...

Person class

Code:
public class Person
{
    // The name of this person.
    private final String name;

    /**
     * Create a new person with the given name.
     * @param name The person's name.
     */
    public Person(String name)
    {
        this.name = name;
    }

    /**
     * @return The person's name.
     */
    public String getName()
    {
        return name;
    }
}
Bid class

Code:
public class Bid
{
    // The person making the bid.
    private final Person bidder;
    // The value of the bid. This could be a large number so
    // the long type has been used.
    private final long value;

    /**
     * Create a bid.
     * @param bidder Who is bidding for the lot.
     * @param value The value of the bid.
     */
    public Bid(Person bidder, long value)
    {
        this.bidder = bidder;
        this.value = value;
    }

    /**
     * @return The bidder.
     */
    public Person getBidder()
    {
        return bidder;
    }

    /**
     * @return The value of the bid.
     */
    public long getValue()
    {
        return value;
    }
}
Lastly the Lot class

Code:
public class Lot
{
    // A unique identifying number.
    private final int number;
    // A description of the lot.
    private String description;
    // The current highest bid for this lot.
    private Bid highestBid;

    /**
     * Construct a Lot, setting its number and description.
     * @param number The lot number.
     * @param description A description of this lot.
     */
    public Lot(int number, String description)
    {
        this.number = number;
        this.description = description;
    }

    /**
     * Attempt to bid for this lot. A successful bid
     * must have a value higher than any existing bid.
     * @param bid A new bid.
     * @return true if successful, false otherwise
     */
    public boolean bidFor(Bid bid)
    {
        if((highestBid == null) ||
               (bid.getValue() > highestBid.getValue())) {
            // This bid is the best so far.
            highestBid = bid;
            return true;
        }
        else {
            return false;
        }
    }
    
    /**
     * @return A string representation of this lot's details.
     */
    public String toString()
    {
        String details = number + ": " + description;
        if(highestBid != null) {
            details += "    Bid: " + 
                       highestBid.getValue();
        }
        else {
            details += "    (No bid)";
        }
        return details;
    }

    /**
     * @return The lot's number.
     */
    public int getNumber()
    {
        return number;
    }

    /**
     * @return The lot's description.
     */
    public String getDescription()
    {
        return description;
    }

    /**
     * @return The highest bid for this lot.
     *         This could be null if there is
     *         no current bid.
     */
    public Bid getHighestBid()
    {
        return highestBid;
    }
}
Any help would be much appreciated!

Thanks.