// This class supports items in the Alberta class.
// Part of the reason for having this class is to show that different
// classes implementing the same interface can be completely unrelated.

import java.util.Hashtable;
public class Catalogue
{
    // A Catalogue is a listing of Item data,
    // that is, a mapping from id to name, base price.
    // Each Item entity can then use the Catalogue to lookup.

    // This variable maps ids to index entries.
    Hashtable index = new Hashtable ();

    // This is number of elements in the Catalogue.
    int numElements = 0;

    // These variables represent the Catalogue.
    // They are indexed from 1; the 0'th element is always null to
    //handle non-entered lookups.
    private String [] names;
    private int [] prices;	// in cents

    // Make a new Catalogue withe some entries.
    public Catalogue ()
    {
	names = new String [100];
	prices = new int [100];

	// These are redundant but make the point.
	names [0] = null;
	prices [0] = 0;
    }

    // This returns the index number of an id, or 0 if none such.
    private int indexNumber (String id)
    {
	Integer entry = (Integer) index. get (id);
	if (entry == null)
	    return 0;
	else
	    return entry. intValue ();
    }

    // Returns the name of an item, or null if no such id.
    public String getName (String id)
    {
	return names [indexNumber (id)];
    }

    // Returns the price of an item, or 0 if no such id.
    public int getPrice (String id)
    {
	return prices [indexNumber (id)];
    }

    // Store data for an id.
    public void put (String id, String name, int price)
    {
	int i = indexNumber (id);
	if (i == 0)
	{
	    // Wasn't there: put a new one.
	    numElements = numElements + 1;
	    i = numElements;
	    index. put (id, new Integer (i));
	}

	names [i] = name;
	prices [i] = price;
    }
}