Calling a superclass method from a subclass

Question

I'm modelling a bank account with a superclass Account and a subclass SavingsAccount that can't be overdrawn. The makeWithdrawal() method, when called from the main class, should check if the withdrawal is greater than the balance and prompt for input, then edit the balance.

How can I call the makeWithdrawal() method from Account and override it in SavingsAccount using the super keyword? My compiler is giving me "error: incompatible types: missing return value.

Method in Account:

double makeWithdrawal(double withdrawal)    {
    return balance -= withdrawal;
}

(Pretty simple.) This method was initially abstract, but it was causing errors.

Method in SavingsAccount:

    public double makeWithdrawal(double withdrawal) {
        double tempbalance = getBalance();
        if (withdrawal > getBalance())  {
            withdrawal = Input.getDouble("Your withdrawal cannot be larger than your balance. Enter a withdrawal <= "+getBalance());
            return;
        }
        else    {
            return super.makeWithdrawal(withdrawal);
            }
    }

Possible duplicate of [Java Polymorphism How to call to super class method for subclass object](https://stackoverflow.com/questions/14907424/java-polymorphism-how-to-call-to-super-class-method-for-subclass-object) — talex, Jul 20 '17 at 16:14
OP, you need to indicate *where* the error occurs. The answer is much simpler than you make it sound. — Mad Physicist, Jul 20 '17 at 16:14
I get the error of missing return value. Or, it says that I can't override the superclass method. — , Jul 20 '17 at 16:15
(Yeah sorry I'm a noob programmer) The error is at the end of the if statement in SavingsAccount — , Jul 20 '17 at 16:16

score 1 · Answer 1 · answered Jul 20 '17 at 16:13

The issue is not with your call to super.makeWithdrawl(), which is correct. It is with the empty return statement in the if clause above it. Your logic to get the update the withdrawal amount is sensible, but you need to return the new balance when you do that. I would recommend just moving the call to super.makeWithdrawl() outside the conditonal:

if(withdrawal > getBalance())  {
    withdrawal = Input.getDouble("Your withdrawal cannot be larger than your balance. Enter a withdrawal <= "+getBalance());
}
return super.makeWithdrawal(withdrawal);

This will use the updated withdrawal amount if the original one was too large.

score 0 · Answer 2 · answered Jul 20 '17 at 16:14

0

in the if

if (withdrawal > getBalance())  {
            withdrawal = Input.getDouble("Your withdrawal cannot be larger than your balance. Enter a withdrawal <= "+getBalance());
            return;
        }

you need to return double value rather than simple returning.

answered Jul 20 '17 at 16:14

Isha Agarwal

420
4
12

Thanks, I'll try this – Jul 20 '17 at 16:17

score 0 · Accepted Answer · answered Jul 20 '17 at 16:15

The problem is with

return;

You should replace it by

return withdrawal;

    public double makeWithdrawal(double withdrawal) {
    double tempbalance = getBalance();
    if (withdrawal > getBalance())  {
        withdrawal = Input.getDouble("Your withdrawal cannot be larger than your balance. Enter a withdrawal <= "+getBalance());
        return withdrawal;
    }
    else    {
        return super.makeWithdrawal(withdrawal);
        }
}

score -1 · Answer 4 · answered Jul 20 '17 at 16:13

-1

If I understood you correctly:

Account is the base class and SavingsAccount the subclass?

then: super.makeWithdrawal(withdrawal);

also make sure you inherit when defining the class:

public class SavingsAccount extends Account{...}

answered Jul 20 '17 at 16:13

0x45

779
3
7
26

1

Does not answer the question. – Mad Physicist Jul 20 '17 at 16:13

Calling a superclass method from a subclass

4 Answers4