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Thread: Help needed for string index out of bounds exception

  1. #1
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    Default Help needed for string index out of bounds exception

    I am fairly new at this and any help would be appreciated . thx

    private static int doFarenheitCelsius()
    {
    util.writeln("\nYou chose Farenheit or Celsius");

    Scanner reader = new Scanner(System.in);
    double temp = 0;

    double convertedF = 0;
    double convertedC = 0;
    DecimalFormat df = new DecimalFormat("#.##");
    util.writeln("Enter a temperature ");
    temp = reader.nextInt();

    String strInput = "0";

    util.writeln("Convert to Farenheit or Celsius");
    strInput = reader.nextLine();
    char letter = strInput.charAt(0);

    if (letter == 'F' && letter == 'f')
    {
    convertedF = temp * 9/5 + 32;
    util.writeln(temp + "is " + df.format(convertedF) + " Degrees Ferenheit");
    }
    else if (letter == 'C' && letter == 'c')
    {
    convertedC = (temp - 32) * 5 / 9;
    util.writeln(temp + "is " + df.format(convertedC) + " Degrees Celsius");
    }

    return 0;

    }
    and my error message is as below, seems like a simple method to execute


    You chose Farenheit or Celsius
    Enter a temperature
    45
    Convert to Farenheit or Celsius
    Exception in thread "main" java.lang.StringIndexOutOfBoundsException: String index out of range: 0
    at java.lang.String.charAt(Unknown Source)
    at exercises.SuperCalculatorAssignmentFive.doFarenhei tCelsius(SuperCalculatorAssignmentFive.java:132)
    at exercises.SuperCalculatorAssignmentFive.main(Super CalculatorAssignmentFive.java:73)


  2. #2
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    Default Re: Help needed for string index out of bounds exception

    Please read the Announcement topic at the top of the sub-forum to learn how to post code in code or highlight tags and other useful info for newcomers.

    The statement:

    temp = reader.nextInt();

    takes the numerical part of the user's input and leaves the linefeed character in the input buffer. Then, the statement:

    strInput = reader.nextLine();

    sees there is still a linefeed in the input buffer and accepts it as the input. The result is that strInput is an empty string with no length, hence the error.

    To correct, flush the buffer after the first statement with a throwaway call to reader:

    reader.nextLine();

    Let me know if this is not clear.

  3. #3
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    Default Re: Help needed for string index out of bounds exception

    reader.nextLine(); must be returning an empty String. Do you press enter or does this just happen immediate after the "Convert to Farenheit or Celsius" text is printed out? If you are pressing enter, there is your problem. If not, I'm not really sure why that would be happening. Perhaps something weird is going on in your util.writeln(String) method which cases the Scanner to think user input occurred.
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  4. #4
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    Default Re: Help needed for string index out of bounds exception

    thanks GregBrannon, that reader.nextLine(); cleared the mismatch error but doesn't do my loop. I'll work on that. and I assume by the link you gave me, I posted incorrectly . Sorry about that thought I was in the right area.

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    Default Re: Help needed for string index out of bounds exception

    You posted in the right area. You didn't post your code using tags to make it readable.
    Improving the world one idiot at a time!

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