check if a long type contains characters

Question

I have a textfield which takes long value and if it takes characters then it should display an error message. Is there any method like isNAN() for long to check whether that variable contains any character?

[What have you tried?](http://whathaveyoutried.com) There are many possible solutions. — jlordo, Jan 23 '13 at 10:36
possible duplicate of [Restricting JTextField input to Integers](http://stackoverflow.com/questions/11093326/restricting-jtextfield-input-to-integers) — assylias, Jan 23 '13 at 10:37
I tried using try/catch. but is there any method like isNAN() to check whether the variable is a number or not — justified, Jan 23 '13 at 10:41

score 1 · Answer 1 · answered Jan 23 '13 at 10:36

1

The static method Long.parseLong() will throw a NumberFormatException if the string does not contain a parsable long.

answered Jan 23 '13 at 10:36

Werner Kvalem Vesterås

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Or even better, prevent the user from entering a non number character with a filter. – assylias Jan 23 '13 at 10:37
1

@justified.. Then catch the exception, and print the message from the properties file there. – Rohit Jain Jan 23 '13 at 10:39

score 1 · Answer 2 · answered Jan 23 '13 at 10:37

1

You can usually do this by trying to do Long.parseLong(textfield.getText()) wrapped by a try catch block where you would catch the NumberFormatException.

If the exception is caught then it means the user didn't enter a valid long value.

answered Jan 23 '13 at 10:37

Dan D.

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score 1 · Answer 3 · answered Jan 23 '13 at 10:38

1

long x = Long.parseLong("12345L");

You should try catch the above statement as it can throw NumberFormatException

answered Jan 23 '13 at 10:38

Xavier DSouza

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score 1 · Answer 4 · answered Jan 23 '13 at 10:40

1

You can have a small utility method like this:

private boolean isLong(String str){
    try{
      Long.parseLong(str);
    }
    catch(NumberFormatException nfe){
      return false;
    }
  return true;
}

answered Jan 23 '13 at 10:40

Priyank Doshi

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score 0 · Answer 5 · answered Jan 23 '13 at 10:43

0

Just as an alternative to other solutions, you can use a regex

    boolean containsCharacters = !txt.matches("-?\\d+");

answered Jan 23 '13 at 10:43

Evgeniy Dorofeev

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check if a long type contains characters

5 Answers5