Question

I’m working on homework and I won’t post the full code but I’m stuck on something that’s probably simple and I can’t find it in my book so I need to be pointed in the right direction.
I’m working with classes and interfaces.

Basically in my main code I have a line like this

    CheckingAccount checking = new CheckingAccount(1.0);  // $1 monthly fee

I was told to create a class called CheckingAccount and in that class I am told “This class should include an instance variable for the monthly fee that’s initialized to the value that’s passed to the constructor.

Since I’m new this is barely english to me and I’m assuming what that is saying is to take that 1.00 fee and declare it in the CheckingAccount class so I can create a method using that variable to calculate something.

soooo… How do I do that? I know how to create an instance variable it would be something like

    public double  monthly fee =

but then what? or I could be wrong. I am really doing bad at this java stuff. Any help is appreciated.

I guess another way to ask it is am I just declaring it as 1.0? or am I “importing” that value in case it changes later at some point you don’t have to go through the code to change it in all of the classes?

Answer 1

Your requirement (as I read it) is to initialize the instance variable in the constructor, and your instantiation (new CheckingAccount(1.0);) shows you are on the right track.

What your class will need is a constructor method which receives and sets that value 1.0.

// Instance var declaration
private double monthly_fee;

// Constructor receives a double as its only param and sets the member variable
public CheckingAccount(double initial_monthly_fee) {
  monthly_fee = inital_monthly_fee;
}