How to resolve NumberFormatException: Empty string?

Question

When I run this program i get the error Exception in thread "main" java.lang.NumberFormatException: empty String. Is it possible to make this work by throwing the exception some how or must I use a try catch statement?

private double[] scores3 = new double[5]; 
Scanner keyboard = new Scanner(System.in);

public void enterData() 
{
   double score;
   double numberMin = 0;
   double numberMax = 100;



do{
    System.out.println("Enter the student's third test score");

      while (!keyboard.hasNextDouble()) {

      keyboard.next();
      }
       score3 = keyboard.nextDouble();


        }
         while  (score3 <= numberMin || score3 >= numberMax);
         double score3 = Double.parseDouble(keyboard.nextLine());

If you throw the exception, it still must be caught and handled somewhere. Just use a try/catch block. — Hovercraft Full Of Eels
– Hovercraft Full Of Eels, Commented Jan 29, 2013 at 19:01
I suggest you step through your code in your debugger as it isn't doing what you think it is doing. The Exception is symptom of a confused program, you are better off fixing the cause. — Peter Lawrey
– Peter Lawrey, Commented Jan 29, 2013 at 19:05
I'm wondering why you parse keyboard.nextLine() and not score3? As far as I can tell, the error you got is there. — Jonathan Drapeau
– Jonathan Drapeau, Commented Jan 29, 2013 at 19:11
You can also use Apache commons StringUtils to check if a string is numeric prior to converting. — CodeChimp
– CodeChimp, Commented Jan 29, 2013 at 19:19

Uluk Biy · Accepted Answer · 2013-09-25 17:06:08Z

1

Before parsing a String to a Number.. compare the string with " " or use isEmpty() function to check if its a empty string or not !

Example:

if (myString.isEmpty()) {
    //Do Nothing
} else {
    //Code to perform calculations
}

or

if (!myString.isEmpty()) {
    //Code to perform calculations
}

edited Sep 25, 2013 at 17:06

Uluk Biy

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answered Jan 29, 2013 at 19:15

c.pramod

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2 Comments

Hovercraft Full Of Eels Over a year ago

This would break for every non-numeric String that doesn't equal " ".

Uluk Biy Over a year ago

Should be myString.trım().isEmpty().

Zylth · Accepted Answer · 2013-01-29 19:14:38Z

0

To your question of if you can throw the error elsewhere, you could do that by declaring

public void enterData() throws NumberFormatException

However I would recommend using a try catch block if you want to continue iterating over your while statements.

answered Jan 29, 2013 at 19:14

Zylth

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1 Comment

Hovercraft Full Of Eels Over a year ago

But if he throws it, he still must handle the thrown exception wherever he calls the method that is throwing it, and thus will need a try/catch block.

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