Question

In my program I have 4 classes like the following:

• class Bank
• class Branch extends Bank
• class Customer extends Branch
• class Loan extends Customer

If I want to add a Customer, then I give all the parameters from main function. like:

customer(bank name, bank add, branch number, brunch add, customer info...)

From this constructor, bank’s information goes to the Bank class via both Customer and Branch constructors using super() and so on.

The problem is when I created the Loan, class extending the Customer class, then I didn’t use any constructor, and I don’t want to use it too, because I want only one variable from the Customer class. But my compiler showing this error, it is saying to use a constructor for taking all the parameters for Bank, Branch, and Customer‘s constructors.

How can I solve this problem without using any constructor in the Loan class?

Answer 1

The simplest way to avoid using the Customer constructor in the Loan class is to not extend Customer. When deciding what class to extend, if any, you should use the “is a” test. For example, a Branch is a Bank, so it makes sense to have class Branch extends Bank. However, Loan is a Customer doesn’t really make sense, so you shouldn’t do class Loan extends Customer. On the other hand, a Customer has a Loan; in fact, a Customer may have more than one Loan or none at all. This means that it makes sense to have a Loan member variable (or perhaps a List of Loans, if you have learned about the Container API) in the Customer class.