try to avoid using the String's replace method...

when using the replace method, additional string object will generate  ,which will burden the GC...
especially when you have many metrics and all your metric values is just number type without `,` , there's no need to using the replace method...

Thousands separators are locale dependent, so if we want include support for them, I think we should rather use the proper locale specific number format parser. We should also make this configurable, since any additional checks may add significant overhead to number parsing, and leave the default to support only correctly formatted values in computerized scientific notation.