Question

A super class Demand has been defined to store the details of the demands for a product. Define a subclass Supply which contains the production and supply details of the products.

The details of the member of both the classes are given below:

Class name	Demand
Data members/instance variables:
pid	string to store the product ID
pname	string to store the product name
pdemand	integer to store the quantity demanded for the product
Methods/Member functions:
Demand(...)	parameterised constructor to assign values to the data members
void display( )	to display the details of the product
Class name	Supply
Data members/instance variables:
produced	integer to store the quantity of the product produced
prate	to store the cost per unit of the product in decimal
Methods/Member functions:
Supply(...)	parameterised constructor to assign values of the data members of both the classes
double calculation( )	returns the difference between the amount of demand  (rate×demand) and the amount produced (rate× produced)
void display( )	to display the details of the product and the difference in amount of demand and amount of supply by invoking the method calculation( )

Assume that the super class Demand has been defined. Using the concept of inheritance, specify the class Supply giving the details of the constructor(...), double calculation() and void display().

Answer 1

class supply extends demand
{
  int produced;
  double prate;
      public supply(int pd, double pr, String prodid,
      String pn, int pdm)
      {
         pproduced=pd;
         prate=pr;
         super(prodid,pn,pdm);
     }
     public double calculation()
     {
      return ((prate*super.pdemand) - (prate*
      produced));
     }
     public void display()
    {
    System.out.println(“Product ID :" , super.pid);
    System.out.println(“Product Name :”, super.
    pname);
    System.out.println(“Product demand :”, super.
    pdemand);
    System.out.println(“Product    Produced    :",
    produced);
    System.out.println(“Product Rate :” ,prate);
    double diff= calculation( );
    System.out.println(“Demand - Supply :", diff);
  }
}