Java charAt() String index out of range: 0

Question

I have this code :

private void submitPstart() {

    if (tStock.getText().charAt(0)>='A' && tStock.getText().charAt(0)<='Z'){


    }else {
        errorBox ("Uppercase A-Z");
    }

    tStock.setText("");
    tStock.setFocus();
}

THis is working but when I try not to put anything on the textbox and press the OK button it crashes. It says:

java.lang.StringIndexOutOfBoundsException: String index out of range: 0

and it pointed out to this part: if (tStock.getText().charAt(0)>='A' && tStock.getText().charAt(0)<='Z')

Any help is appreciated. Thanks

Brian Agnew · Accepted Answer · 2012-10-29 09:31:40Z

7

You need to check if getText() returns a 0-length (i.e. empty) string.

If it does, then don't try to pull the first character out! (via charAt())

Note that your commented-out check for length() should occur prior to the existing character check.

You may want to check for a null string being returned as well, depending on your framework/solution etc. Note the Apache Commons StringUtils.isEmpty() method, which performs this check concisely.

edited Oct 29, 2012 at 9:31

answered Oct 29, 2012 at 9:19

Brian Agnew

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Comments

Brian Agnew · Accepted Answer · 2012-10-29 11:15:37Z

3

you must check null and length greater than 0.

 if (tStockPIStart!=null && tStockPIStart.getText().length()>0 && tStockPIStart.getText().charAt(0)>='A' && tStockPIStart.getText().charAt(0)<='Z'){

edited Oct 29, 2012 at 11:15

Brian Agnew

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answered Oct 29, 2012 at 9:21

Subhrajyoti Majumder

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4 Comments

user1782426 Over a year ago

what if sir for example I enter a lower case letter and want it to conver to upper case?

Subhrajyoti Majumder Over a year ago

you can do two thing 1. add lower case condition or 2. use equalsignorecase.

Subhrajyoti Majumder Over a year ago

if (tStockPIStart!=null && tStockPIStart.getText().length()>0 && "A".equalsIgnoreCase(""+tStockPIStart.getText().charAt(0)) && "Z".equalsIgnoreCase(""+tStockPIStart.getText().charAt(0))){}

Brian Agnew Over a year ago

I think it would make life easier if tStockPIStart.getText() was extracted into a variable

Sujay · Accepted Answer · 2012-10-29 09:21:06Z

2

Try

if (tStockPIStart.getText().length() > 0 && tStockPIStart.getText().charAt(0)>='A' && tStockPIStart.getText().charAt(0)<='Z')

In your case, if the text is empty, then the length returned will be 0. Hence the charAt(..) method will throw you an exception. As such, you should first check that the text that you're trying to compare is empty or not.

answered Oct 29, 2012 at 9:21

Sujay

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2 Comments

user1782426 Over a year ago

thanks for this sir. i also tried this one and its working :)

user1782426 Over a year ago

what if sir for example I enter a lower case letter and want it to conver to upper case?

koljaTM · Accepted Answer · 2012-10-29 09:21:09Z

2

Add

if (tStockPIStart!=null && tStockPIStart.length>0) {
    [...]
}

answered Oct 29, 2012 at 9:21

koljaTM

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Comments

RNJ · Accepted Answer · 2012-10-29 09:28:30Z

0

In Java 7 there is the isEmpty method you can use to make things a bit more expressive in your code

if (tStockPIStart.getText()!=null && !tStockPIStart.getText().isEmpty()) {
    //do stuff
}

This is the same as doing length != 0 but I personally think is a bit more clear.

answered Oct 29, 2012 at 9:28

RNJ

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