Question

I just wrote this simple methode that must return a double value. It’s a function to withdraw money from the bank account. The function must let the user get the money only if he entries a value smaller than his the amount of money he has in his account.
There is a condition where, if he is a special user, he can take the money even if he tries a value = balance+1000.

As I’m a beginner to java, I’m not yet familiar with this thing of types (I’m a php programmer, so I never really had to worry about this, but I’m getting troubles to make this code work, because I’m returning a double, if it’s ok, but a false, if it’s not, and I can’t do this in java.. This is my methode.. (the variables ‘balance’ and ‘special’ belongs to my class).

public double getMoney (double value) {
    if (value <= balance) {
        balance = balance - value;
    } else {
        if (special == true && value < (balance+1000)) {
            return balance-value;
        } else {
            return false;
        }
    }
}

I know it’s a noob question, but I just started studying java and I was used to code using PHP, where I don’t need to worry about the type of my variables, so I was wondering if you could give me some advices.
Thanks

Answer 1

You could return Double.NEGATIVE_INFINITY, instead of false.
Then the caller explictly checks for that value, and detects ist as invalid withDrawn().

The caller checks that by

double val = getMoney(5000000);
if (val == Double.NEGATIVE_INFINITY) {
   // money could not be withdran
   // print message
} else {
   // ok money could be withdrawn
}

If you want to do that more professional you would have to retun a transactionInfo:

TransActionInfo info = getMoney(500000);
if (info.getStatus == Status.LIMIT_EXCEEDED) {
   // could not withraw

} else {
   ...
}

Instead of the if you could use a switch statement:

TransActionInfo info = getMoney(500000);
switch (info.getStatus()) {
  case: Status.OK: 
     break;
  case Status.LIMIT_EXCEEDED:
    // inform on display of bankomat. or similar
     break;
  ...
}