How to check if a String is number, not a word?

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www - 24 Jul 2007 21:09 GMT

Hi,

I need to check if a String is number, like "24.48936" or "-1.54774",
not "weight", or "length". How can I do that?

I know it need regular expression. But I am not good at it. Could you
help me?

Thank you.

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Oliver Wong - 24 Jul 2007 21:49 GMT

> Hi,
>
[quoted text clipped - 3 lines]
> I know it need regular expression. But I am not good at it. Could you
> help me?

Step 1: Define the exact rules for determining whether or not a given
string is a "number", depending on what your definition of number is. E.g.
is "five" a number? What about "XXIV"? Is any string containing solely
digits a number (e.g. "00000")? Does the presence of whitespace mean it's
not a number (e.g. " 12 ")? Etc.

Step 2: Post your rules, and we can help you with the regular
expression part.

- Oliver

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Jasdeep - 25 Jul 2007 07:47 GMT

> > Hi,
>
[quoted text clipped - 14 lines]
>
> - Oliver

Try This Code:

/**
*patteren to match whether entered number is 3 or less digits
followed by dot followed by 3 or *less digits
*/
String decimalPattern = "(\\d{1,3})?(.)?(\\d{1,3})?";

/**
*patteren to match whether entered number 3 digit integer
*/

String integerPattern="(\\d{1,3})";

String stringYouEntered="545.12";

boolean matchResult=false;

if(stringYouEntered.contains(".")){
matchResult=stringYouEntered.matches(decimalPattern);
}else{
matchResult=stringYouEntered.matches(integerPattern);
}

if(matchResult){
System.out.prinln("I Got It Right, Number you Entred matches my
patteren");
}

.. It works for me.. Hope it will help you...

-Jasdeep

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Steve Wampler - 24 Jul 2007 22:08 GMT

> Hi,
>
[quoted text clipped - 3 lines]
> I know it need regular expression. But I am not good at it. Could you
> help me?

You can do it without a regular expression if you want:

public static boolean method isNum(String s) {
try {
Double.parseDouble(s);
}
catch (NumberFormatException nfe) {
return false;
}
return true;
}

Of course, you're likely to be better off directly using the result
of parseDouble() as you're likely to need the result if it *is*
a number.

Signature

Steve Wampler -- swampler@noao.edu
The gods that smiled on your birth are now laughing out loud.

Reply to this Message

Knute Johnson - 24 Jul 2007 22:25 GMT

> Hi,
>
[quoted text clipped - 5 lines]
>
> Thank you.

If they are always going to be floating point numbers as in your
example, use Integer.parseDouble() and if it throws a
NumberFormatException it isn't a number.

Signature

Knute Johnson
email s/nospam/knute/

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Steve Wampler - 24 Jul 2007 22:47 GMT

>> I need to check if a String is number, like "24.48936" or "-1.54774",
>> not "weight", or "length". How can I do that?
>...
> If they are always going to be floating point numbers as in your
> example, use Integer.parseDouble() and if it throws a
> NumberFormatException it isn't a number.

This should for integer values as well (though I think you mean
Double.parseDouble()).

Signature

Steve Wampler -- swampler@noao.edu
The gods that smiled on your birth are now laughing out loud.

Reply to this Message

Knute Johnson - 24 Jul 2007 22:57 GMT

>> Hi,
>>
[quoted text clipped - 9 lines]
> example, use Integer.parseDouble() and if it throws a
> NumberFormatException it isn't a number.

Make that Double.parseDouble(). Integer.parseDouble() will get you no
where :-).

Signature

Knute Johnson
email s/nospam/knute/

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How to check if a String is number, not a word?

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