Java Regex for Decimal values

[Sekhar Nat]

I've writing a regex for validating decimal values.

These are the conditionals:
Decimal values can have a + or -
The value can have either a dot or a comma as the decimal separator
The maximum number of digits before the decimal separator is 8
The maximum number of digits after the decimal separator is 3

This is the regex i've written but it somehow doesn't seem to work..I'm writing this inside a Inputfilter in android and matcher.matches() returns true for 999999999 etc.

Pattern mPattern = Pattern.compile("[\\+\\-]?[0-9]{0,8}[,|.]?[0-9]{0,3}");

What is the problem with this regex?

Thank you

[Stephan van Hulst]

It matches 8 digits, then it matches no separator, and then it matches another digit. The separator should not be optional if there's a fractional part.

[Campbell Ritchie]

Look in the documentation for java.util.Scanner and you will find some regexes there.

[Sekhar Nat]

Thanks Stephen. This works now.

 Pattern mPattern = Pattern.compile("[\\+\\-]?[0-9]{0,8}([,|.][0-9]{0,3})?");

@Campbell. Thanks. Just looked at how scanner.nextDouble() works.

[Campbell Ritchie]

Well done

[Darryl Burke]

You don't need the pipe character between the comma and dot in that character class. Not unless the pipe character (which is not a metacharacter inside a character class) is also acceptable as a decimal delimiter.

As it stands, your regex will match "9999|99" which is probably not what you want.

[Richard Tookey]

Sekhar Nat wrote:Thanks Stephen. This works now.

 Pattern mPattern = Pattern.compile("[\\+\\-]?[0-9]{0,8}([,|.][0-9]{0,3})?");

I don't see why the \\ pairs are needed?

[Sekhar Nat]

I think it is not necessary. [+-] should do good. Take a look at this.

[Sekhar Nat]

@Darryl. Yes you are right. Pipe character isn't necessary. Thanks