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[Java] How To Check if a String is a Valid Number?

If you are someone new to Java and would like to check if a String is a valid number or not, this post will help you get answer to your question.

Below is the coded snippet with explanation for checking out if a string is a valid number. The below mentioned code is written in Java.

In the below mentioned code snippet, i declared an integer called isThisANumber , this integer will be used to save the parsed Integer. Static method parseInt( ) of the Integer class has been used to attempt to convert the string parameter into an Integer. In case if the string is not a valid integer and throws up parsing issues while converting, NumberFormatException is thrown.

int isThisANumber = 0;
try
{
isThisANumber = Integer.parseInt(someStringToTest); 
}
catch (NumberFormatException nfe)
{
System.out.println("This string is not a valid number."); //Oops..not a valid int
}

 

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This entry was posted on Tuesday, December 16th, 2008 at 9:37 am and is filed under Java. You can follow any responses to this entry through the RSS 2.0 feed. You can leave a response, or trackback from your own site.

4 Responses to “[Java] How To Check if a String is a Valid Number?”

  1. What nonsense. Either you don’t know English/mathematics, or you don’t know Java.

    If I initialize:

    String someStringToTest = “12.345″;

    Is 12.345 a number?
    What will your code snippet say?

    If this is the extent of your competency, perhaps you shouldn’t be dishing out “advice” on programming.

  2. Here you try this,

    String someStringToTest = “12.345″;
    Double stringToDouble = null;

    if ( someStringToTest.matches(“\\d*\\.\\d*”) )

  3. Here you try this,

    String someStringToTest = “12.345″;
    Double stringToDouble = null;

    if ( someStringToTest.matches(”\\d*\\.\\d*”) )
    stringToDouble = Double.parseDouble(someStringToTest);

  4. Bala’s snippet is a nice way to do it and definitely makes sense. I do not see why you have to be mean about his English/mathematics.

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