sale.java

java编程代码

/**
 Class for a simple sale of one item with no tax, discount, or other adjustments.
 Class invariant: The price is always nonnegative; the name is a nonempty string.
*/
public class Sale
{
    private String name; //A nonempty string
    private double price; //nonnegative

    public Sale( )
    {
        name = "No name yet";
        price = 0;
    }

    /**
     Precondition: theName is a nonempty string; thePrice is nonnegative.
    */
    public Sale(String theName, double thePrice)
    {
        setName(theName);
        setPrice(thePrice);
    }

    public Sale(Sale originalObject)
    {
        if (originalObject == null)
        {
            System.out.println("Error: null Sale object.");
            System.exit(0);
        }
        //else
        name = originalObject.name;
        price = originalObject.price;
    }

    public static void announcement( )
    {
        System.out.println("This is the Sale class.");
    }

    public double getPrice( )
    {
        return price;
    }

   /**
     Precondition: newPrice is nonnegative.
    */
    public void setPrice(double newPrice)
    {
        if (newPrice >= 0)
            price = newPrice;
        else
        {
            System.out.println("Error: Negative price.");
            System.exit(0);
        }
    }

    public String getName( )
    {
        return name;
    }

    /**
     Precondition: newName is a nonempty string.
    */
    public void setName(String newName)
    {
        if (newName != null && newName != "")
            name = newName;
        else
        {
            System.out.println("Error: Improper name value.");
            System.exit(0);
        }
    }

    public String toString( )
    {
        return (name + " Price and total cost = $" + price);
    }

    public double bill( )
    {
        return price;
    }

    /*
     Returns true if the names are the same and the bill for the calling
     object is equal to the bill for otherSale; otherwise returns false.
     Also returns false if otherObject is null.
    */
    public boolean equalDeals(Sale otherSale)
    {
        if (otherSale == null)
            return false;
        else
            return (name.equals(otherSale.name)
                && bill( ) == otherSale.bill( ));
    }

    /*
     Returns true if the bill for the calling object is less
     than the bill for otherSale; otherwise returns false.
    */
    public boolean lessThan (Sale otherSale)
    {
        if (otherSale == null)
        {
            System.out.println("Error: null Sale object.");
            System.exit(0);
        }
        //else
        return (bill( ) < otherSale.bill( ));
    }

    public boolean equals(Object otherObject)
    {
        if (otherObject == null)
            return false;
        else if (getClass( ) != otherObject.getClass( ))
            return false;
        else
        {
            Sale otherSale = (Sale)otherObject;
            return (name.equals(otherSale.name)
               && (price == otherSale.price));
        }
    }

    public Sale clone( )
	{
	    return new Sale(this );
    }
}