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Thread: Help in looping

  1. #1
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    Default Help in looping



    So, here's my code. I have a runtime error and I think there's a problem in the loop in it but I can't figure it out.



     import java.util.Scanner;
        public class BankSystem
       {
           public static void main(String[] args)
          {
             double acc=1000,d,w;
             int exit, selector;
             char enter;	
             Scanner keyboard = new Scanner(System.in);
             System.out.println("To use the bank system, select 'y' or any other letter to exit.");
             enter = keyboard.nextLine().charAt(0);
             while (enter == 'y')
             {
                System.out.println("Enter one of the following options:");
                System.out.println(" * '1' for account balance.");
                System.out.println(" * '2' for withdraw.");
                System.out.println(" * '3' for deposit.");
                selector = keyboard.nextInt();
                switch (selector)
                {
                   case 1:
                      System.out.println("Your balance is: "+acc);
                      break;
                   case 2:
                      System.out.println("Enter the amount to withdraw.");
                      w = keyboard.nextDouble();
                      if (w<=0 || w>acc)
                         System.out.println("Wrong input.");
                      else
                         acc=acc-w;
                      System.out.println("The selected amount has been withdrawed from your account successfully.");
                      break;
                   case 3:
                      System.out.println("Enter the amount to deposit.");
                      d=keyboard.nextDouble();
                      while (d<=0)
                      {
                         System.out.println("Wrong input.");
                         System.out.println("Enter the right amount.");
                         d = keyboard.nextDouble();
                      }
                      acc=acc+d;
                      System.out.println("The selected amount has been deposited into your account successfully.");
                      break;
                   default:
                      System.out.println("Wrong selection.");
                }
                System.out.println("To continue using the system, select 'y' or any other letter to exit.");
                enter = keyboard.nextLine().charAt(0);
             }
             System.out.println("System is shutting down...");
          }
       }



    Any help or hints on how to correct my error would be great. Thanks.





  2. #2
    Senile Half-Wit Freaky Chris's Avatar
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    Default Re: Help in looping

    Whats the runtime error?
    chris[at]javaprogrammingforums[dot]com

    Prifysgol Bangor University, North Wales

  3. #3
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    Default Re: Help in looping

    Quote Originally Posted by Freaky Chris View Post
    Whats the runtime error?

    Exception in thread "main" java.lang.StringIndexOutOfBoundsException: String index out of range: 0
    at java.lang.String.charAt(String.java:686)
    at BankSystem.main(BankSystem.java:49)

  4. #4
    Senile Half-Wit Freaky Chris's Avatar
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    Default Re: Help in looping

    Clear the input buffer before reading the nextLine, nexInt leaves a \n character in the buffer. Meaning that when you do nextLine no input is read from the user and an empty String is returned thus, when you try to get the letter at 0 you get the exception because the String doesn't have a length of 1, it has a length of 0.

    Chris
    chris[at]javaprogrammingforums[dot]com

    Prifysgol Bangor University, North Wales

  5. The Following User Says Thank You to Freaky Chris For This Useful Post:

    endframe (December 28th, 2010)

  6. #5
    Member goldest's Avatar
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    Wink Re: Help in looping

    Hey endframe,

    The problem here is that, your nextLine() method is trying to read till the end of the line and going to the beginning of second line. And because of that, it is reaching the 1st index. When we enter a single option, we are providing a 0 index value. And this is where the exception is coming from.

    Solution would be to use the simple next() method instead of nextLine() method. So you have to ultimately change two lines of code where you are taking the input options from the console.

    Change your,
    enter = keyboard.nextLine().charAt(0);
    to
    enter = keyboard.next().charAt(0);
    After this the runtime error will be gone. What this does is, it returns the next String token and takes the 0 index value, which is the option we provide.

    Hope that helps,

    Goldest
    Java Is A Funny Language... Really!

    Sun: Java Coding Conventions

    Click on THANKS if you like the solution provided.
    Click on Star if you are really impressed with the solution.

  7. The Following User Says Thank You to goldest For This Useful Post:

    endframe (December 28th, 2010)

  8. #6
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    Default Re: Help in looping

    Thanks guys, it worked and now I understand what was wrong.
    Best wishes to all.

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