Method Retrieval and Inheritance Confusion

Question

Ok,so I am getting a lot of trouble, I am still learning Java and my book has set me a task that I find common over the net, the part that I am stuck on is...

I must create a bank account program, an account holder is given a savings account (which has an interest rate and no overdraft facility), and a checking account (which has an overfraft facility of £100 and no interest).

I am not implementing the overdraft yet and am only half way to getting the withdraw and deposit function ready but my question is with the interest, I have defined in my superclass the savings account balance and the checking account balance so when working out my interest in the savings account class I cannot reference savebalance as I have made it private. I am trying to use the set.name method but i am clearly doing it wrong....

A big smile and a thank you for any one who can help or give advice!

Superclass is as follows:

public class BankDetails
    {
        private String customer;
        private String accountno;
        private double savebalance;
        private double checkbalance;


//Constructor Methods

 public BankDetails(String customerIn, String accountnoIn, double savebalanceIn, double checkbalanceIn)
        {
            customer = customerIn;
            accountno = accountnoIn;
            savebalance = savebalanceIn;
            checkbalance = checkbalanceIn;
        }

      // Get  name
      public String getcustomername()
        {
            return (customer);
        }

      // Get account number
      public String getaccountnumber()
        {
            return (accountno);
        }

       public double getcheckbalanceamount()
        {
            return (checkbalance);
        }

       public double getsavebalanceamount()
        {
            return (savebalance);
        }


public void savewithdraw(double savewithdrawAmountIn)

  {
        savebalance = savebalance - savewithdrawAmountIn;

  }

public void checkwithdraw(double checkwithdrawAmountIn)

  {
        checkbalance = checkbalance - checkwithdrawAmountIn;

  }


 public void savedeposit(double savedepositAmountIn)

  {
        savebalance = savebalance - savedepositAmountIn;

  }

public void checkdeposit(double checkdepositAmountIn)

  {
        checkbalance = checkbalance - checkdepositAmountIn;

  }




    } // End Class BankDetails

Sub Class is as follows:

    import java.util.*; 

public class Savings extends BankDetails
  {

      private String saveaccount;
      private double interest;


      public Savings(String customerIn, String accountnoIn, float interestIn, 
      String saveaccountIn, double savebalanceIn)
        {


            super (customerIn, accountnoIn, savebalanceIn, interestIn);


            saveaccount = saveaccountIn;
            interest = interestIn;

        }


      public String getsaveaccountno()
       {
           return (saveaccount);
       }

      public double getinterestamount()
       {
           return (interest);
       }


      public void interestamount(String[] args)

       {
           BankDetails.getsavebalanceamount(savebalance);
           interest = (savebalance / 100) * 1.75;


       }


       }

Answer 1

Use the superclass's getSaveBalance() method to access the balance (which is suspiciously-named, since you have a savings account class, but keep the balance elsewhere).

(Currently it's getsavebalanceamount(), I assume a renaming to keep with Java conventions.)

---

I'd recommend using consistent CamelCase when naming your getters and setters, e.g., getInterestAmount(), getSaveAccountNo(), etc.

I recommend against commenting simple getters/setters, but if you do, use Javadoc conventions, e.g.:

/** Returns current savings account balance. */
public double getSaveBalance() { ... etc ... }

I also recommend avoid unnecessary parentheses, as currently in your getters, e.g.:

public double getSaveBalance() {
    return saveBalance; // No parens required.
}

Answer 2

I suggest you do something like this,

interface Account{
  int getAccountNumber();
  float getBalance();
}

public class SavingAccount implements Account, Interest{
  int accountNumber;
  public int getAccountNumber(){
    return accountNumber;
  }
  float balance;
  public float getBalance(){
    return balance;
  }
  float savingInterestRate;
  public float getInterestRate(){
     return savingInterestRate;
  }
}

public class CheckingAccount implements Account, OverDraft{
  int accountNumber;
  public int getAccountNumber(){
  return accountNumber;
  }
  float balance;
  public float getBalance(){
    return balance;
  }
}

interface Interest{
  float getInterestRate();
}

interface OverDraft{
....
}