模式匹配器有效数字java

Question

I want to have a number validation. Rules are:

1. A number can start with + or - or nothing (it is taken as a positive number)
2. Cannot start with 0
3. Can have a fraction either . or ,
4. Cannot end with 0

So acceptable numbers are: +123, -123, 123, 1023, 123.03, 123,03. Non acceptable numbers are: 001, 1.000, any letters

I give you the expression that I ve built so far, on Dan's Tools. I have managed almost everything, except expressions after the the fraction. Every help is acceptable.

Expression: (^(\\+|-?)([1-9]+))([0-9]+)(\\.|,?)

Thanks in advance Nikos

Answer 1

Except the fractional part that is missing in your pattern, your regex won't match single digit numbers as you quantified [1-9] and [0-9] with + quantifier requiring at least one char.

You can use

^[+-]?[1-9][0-9]*(?:[.,][0-9]*[1-9])?$

See the regex demo and the regex graph :

Details

• ^ - start of string
• [+-]? - an optional + or -
• [1-9] - a single non-zero digit
• [0-9]* - zero or more digits
• (?:[.,][0-9]*[1-9])? - an optional fractional part: . or , and then zero or more digits followed with a single non-zero digit
• $ - end of string.