Java REGEX for numbers 1 to 100

Question

I'm trying to write a REGEX to accept only numbers between 1-100. It would be great if it accepted everything from 1 to infinity, but that's probably to complex - or impossible.

public static boolean isNumeric(String str) {
return str.matches("-?\\d+(\\.\\d+)?");
}//end boolean.

Why do you want to use regex for this task? Just convert `str` to an `int`, and check for range. That would be far easier. — Rohit Jain, Jan 16 '14 at 19:50
@RohitJain as mentioned below, that may cause an exception to be thrown. — marisbest2, Jan 16 '14 at 20:14

score 3 · Accepted Answer · answered Jan 16 '14 at 19:53

3

It would be great if it accepted everything from 1 to infinity, but that's probably to complex - or impossible.

How about simply "[1-9]\\d*"?

This would accept a non-zero digit followed by any sequence of digits. In other words, any positive integer.

answered Jan 16 '14 at 19:53

NPE

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951
1,012

Quick thought, since the input is a String, it might contain a String of 0's on start, like "007", maybe a better answer would be: `0*[1-9]\\d*` – Jorge Jan 16 '14 at 20:46

takendarkk · Answer 2 · 2014-01-16T20:36:38.900

3

public static boolean isNumeric(String str) throws NumberFormatException {
    int i = Integer.parseInt(str); 
    return i > 0 && i < 100; //Arbitrary numbers within range of int
}

Not using regex but this should accomplish the same thing. Turn the string into an integer, then check to see if it is in the range you want.

edited Jan 16 '14 at 20:36

answered Jan 16 '14 at 19:54

takendarkk

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This would throw an exception if the string contains a non-numeric character. – Dodd10x Jan 16 '14 at 19:57
2

Parsing two times is not necessary, and wrap it in a try catch with the `NumberFormatException` and if at all OP wants to have infinity Integer may overflow. – RP- Jan 16 '14 at 20:01
Both comments are totally true, this was just a quick and dirty example to get him pointed in a direction that might help. I will edit to fix those problems soon. – takendarkk Jan 16 '14 at 20:06

score 1 · Answer 3 · answered Jan 16 '14 at 20:09

1

If you want to be really thorough, you can use "-?(0|([1-9][0-9]*))\.?[0-9]*" which should give you all numbers from -infinity to +inifinity. Getting rid of the -? will give you all positive numbers. "0|(-?[1-9][0-9]*)" should give you all integers from -infinity to +infinity. "[1-9][0-9]*" will give you all integers greater than 0.

answered Jan 16 '14 at 20:09

marisbest2

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Do you know how to limit this to a range including negatives? For example -100 to +100? – James Mar 18 '20 at 00:02

Java REGEX for numbers 1 to 100

3 Answers3