Beginners Java (Loops) - Missing return statement

Question

import java.util.Scanner;

public class Vending {
    public double vend(double balance) {
        Scanner in = new Scanner(System.in);
        balance = 0;
        System.out.print("Enter a command = ");
        String command = in.nextLine();

        while (in.hasNext()) {
            if (command.equals("penny")) {
                balance = balance + 0.01;
                System.out.println("balance = " + balance);
            }
            return balance;
        }
    }
}

Hi! I have tried everything to figure out why the return statement is not being recognized. If I put the "return balance" anywhere else it says that the system.out.println is unreachable... Can any of you kindly help me out as to why this may not be working?? Thank you!!

Your code would be much easier to understand - both for you and us - if you would indent it. If you're using an IDE like Eclipse, you can probably ask it to reformat your source code for you. Once you've done that, the answer may be much more obvious. (I suspect I know what's wrong already, but I want you to reformat the code and see if you can find it yourself.) — Jon Skeet
– Jon Skeet, Commented Mar 15, 2013 at 20:15
I thought it was faster to indent it myself than to ask the OP to do it :) — Cyrille Ka
– Cyrille Ka, Commented Mar 15, 2013 at 20:16
It seems like there is a logic issue. You have to re-read the new line every loop as opposed to reading it once and expecting the loop to work as intended. — user1181445
– user1181445, Commented Mar 15, 2013 at 20:16
That said, accidentally I removed the actual question... Fixed now, sorry for that. — Cyrille Ka
– Cyrille Ka, Commented Mar 15, 2013 at 20:18

Luiggi Mendoza · Accepted Answer · 2013-03-15 20:16:04Z

3

The return statement is inside the while loop and outside the if condition segment, so the code its breaking the loop on the first iteration.

Possible solution: move the return outside the while

while (in.hasNext()) {
    if (command.equals("penny")) {
        balance = balance + 0.01;
        System.out.println("balance = " + balance);
    }
}
return balance;

answered Mar 15, 2013 at 20:16

Luiggi Mendoza

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2 Comments

Betty Jones Over a year ago

Hi! I've tried moving the return outside the while but then I get "Exception in thread "main" java.lang.NoSuchMethodError:main" , when I left all else constant. Do you know what may be the problem then?

Luiggi Mendoza Over a year ago

@BettyJones well, you fixed the vend method problem. Now, make sure you have declared the main method as public static void main(String[] args). If you have a new problem, it would be better to post a new question.

Sotirios Delimanolis · Accepted Answer · 2013-03-15 20:24:04Z

Your method vend(double balance) is defined to return a double. Whatever happens within the method, it must return a double. Now you have a return statement here:

while (in.hasNext()) {
    if (command.equals("penny")) {
        balance = balance + 0.01;
        System.out.println("balance = " + balance);
    }
    return balance;
}

But what happens if your statement in.hasNext() returns false? Then the return inside it will never be reached. Therefore the compiler can not guarantee that your method is valid java and is therefore complaining.

You should add a return statement outside the while.

When you say

If I put the "return balance" anywhere else it says that the system.out.println is unreachable

You put the return statement right before a System.out.println() statement. When a method returns, it gives up on anything that might've happened after the return statement, basically making anything after it useless. The return statement must be the last statement in some execution branch of your method.

Blake · Accepted Answer · 2013-03-15 20:17:49Z

0

That's because the compiler can't guarantee that the return statement will execute because it is within your loop. It has to assume that in.hasNext() may return false and never hit that return.

answered Mar 15, 2013 at 20:17

Blake

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Comments

Grambot · Accepted Answer · 2013-03-15 20:18:11Z

0

You're getting the "Missing return statement" error because there is a possiblity that your while loop is never executed. This leads to the program reaching the end of the function without ever returning.

while (in.hasNext()) {
  if (command.equals("penny")) {
    balance = balance + 0.01;
    System.out.println("balance = " + balance);
  }
  return balance;
}

If we pretend in never has any lines then the program passes the while and therefore the return causing this issue. For your case you can probably just have a default return such as return 0; or however you'd like to handle the situation.

answered Mar 15, 2013 at 20:18

Grambot

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