Java - regex for ordinary positive negative number

Question

I read a lot of regex question, but I didn't find this yet..

I want a regex in Java to check whether a string (no limit to length) is a number:

• including negative (-4/-123)

• including 0

• including positive (2/123)

• excluding + (+4/+123)

• excluding leading zero 0 (05/000)

• excluding . (0.5/.4/1.0)

• excluding -0

This is what I have done so far:

^(?-)[1-9]+[0-9]*

Answer 1

The is a optional -

-?

The number must not start with a 0

[1-9]

it may be followed by an arbitraty number of digits

\d*

0 is an exception to the "does not start with 0 rule", therefore you can add 0 as alternative.

Final regex

-?[1-9]\d*|0

java code

String input = ...

boolean number = input.matches("-?[1-9]\\d*|0");