How to use method return from another Java class

Question

I have this method in a 'BankAccount.java' class

  public double calculateInterest()
  {
    double myInterest = 0.0;
    if(myBalance > 0.0){
    myInterest = this.myBalance * (myInterestRate/12.0);
  }
  return myInterest;
}

I need to use this method in my other class such as:

SavingsAccount extends BankAccount

      if(this.myBalance > 0)
      {  
          System.out.println(calculateInterest());
          this.myBalance += super.calculateInterest();
          this.myBalance -= this.myMonthlyServiceCharges;
      }

Why cannot I do

   this.myBalance += super.calculateInterest();

it is returning as 0.0

when it should be returning around 0.4

Any help would be great, thank you

it works if I put this code in my SavingsAccount class

public double calculateInterest()
{
  double myInterest = 0.0;
  if(myBalance > 0.0){
     myInterest = this.myBalance * (myInterestRate/12.0);
  }
  return myInterest;
  }

But it doesn't really teach me how to use the abstract class properly

Answer 1

Works for me. Here I reproduce with the following

public class BankAccount {

    protected double myBalance = 0;
    protected double myInterestRate = .6;

    public double calculateInterest() {
        double myInterest = 0.0;
        if (myBalance > 0.0) {
            double myInterestRate;
            myInterest = this.myBalance * (this.myInterestRate / 12.0);
        }
        return myInterest;
    }
}

And then....

public class SavingsAccount extends BankAccount {

    double myMonthlyServiceCharges = 1;

    public static void main(String[] args) {
        SavingsAccount sa = new SavingsAccount();
        sa.myBalance = 14;
        sa.doIt();
    }

    void doIt() {
        if (this.myBalance > 0) {
            System.out.println(super.calculateInterest());
            this.myBalance += super.calculateInterest();
            this.myBalance -= this.myMonthlyServiceCharges;
        }
    }

}

Can you try that and see if it works for you?