// Implementation of the Point-of-Sale Terminal (POST) System in JAVA

import java.util.*;

// Class Payment
public class Payment
{
	private float amount;
	public Payment( float cashTendered )
	{
		 this.amount = cashTendered;
	}
	public float getAmount()
	{
		 return amount;
	}
}

// Class ProductCatalog
public class ProductCatalog
{
	 private Hashtable productSpecifications = new Hashtable();
	 public ProductCatalog()
	 {
			ProductSpecification ps = new ProductSpecification( 100,1,"product1");
			productSpecifications.put( new Integer( 100 ), ps );
			ps = new ProductSpecification( 200,1,"product2" );
			productSpecifications.put( new Integer( 200 ), ps );
	 }
	 public ProductSpecification getSpecification( int upc )
	 {
			return (ProductSpecification)
				   productSpecifications.get( new Integer( upc ));
	 }
}

// Class POST
class POST
{
	 private ProductCatalog productCatalog;
	 private Sale sale;
	 public POST( ProductCatalog catalog )
	 {
			productCatalog = catalog;
	 }
	 public void endSale()
	 {
			sale.becomeComplete();
	 }
	 public void enterItem( int upc, int quantity )
	 {
			if ( isNewSale() )
				 sale = new Sale();
			ProductSpecification spec = productCatalog.getSpecification( upc );
			sale.makeLineItem( spec,quantity );
	 }
	 public void makePayment( float cashTendered )
	 {
			sale.makePayment( cashTendered );
	 }
	 private boolean isNewSale()
	 {
			return (( sale==null ) || ( sale.isComplete() ));
	 }
}

// Class ProductSpecification
public class ProductSpecification
{
	 private int upc = 0;
	 private float price = 0;
	 private String description = "";
	 public ProductSpecification( int upc, float price, String description )
	 {
			this.upc = upc;
			this.price = price;
			this.description = description;
	 }
	 public int getUPC()
	 {
			return upc;
	 }
	 public float getPrice()
	 {
			return price;
	 }
	 public String getDescription()
	 {
			return description;
	 }
}

// Class Sale
class Sale
{
	 private Vector lineItems = new Vector();
	 private Date date = new Date();
	 private boolean isComplete = false;
	 private Payment payment;
	 public float getBalance()
	 {
			return payment.getAmount() - total();
	 }
	 public void becomeComplete()
	 {
			isComplete = true;
	 }
	 public boolean isComplete()
	 {
			return isComplete;
	 }
	 public void makeLineItem( ProductSpecification spec, int quantity )
	 {
			lineItems.addElement( new SaleLineItem( spec,quantity ));
	 }
	 public float total()
	 {
			float total = 0;
			Enumeration e = lineItems.elements();
			while ( e.hasMoreElements() )
			{
				 total += ((SaleLineItem)e.nextElement()).subtotal();
			}
			return total;
	 }
	 public void makePayment( float cashTendered )
	 {
			payment = new Payment( cashTendered );
	 }
}

// Class SaleLineItem
class SaleLineItem
{
	 private int quantity;
	 private ProductSpecification productSpec;
	 public SaleLineItem( ProductSpecification spec, int quantity )
	 {
			this.productSpec = spec;
			this.quantity = quantity;
	 }
	 public float subtotal()
	 {
			return quantity*productSpec.getPrice();
	 }
}

// Class Store
class Store
{
	 private ProductCatalog productCatalog = new ProductCatalog();
	 private POST post = new POST( productCatalog );
	 public POST getPOST()
	 {
			return post;
	 }
}