How to add a user-defined string to a regular expression

Question

Hi, I am checking a text box that should only accept float. I use this regex

^(?:[1-9]\\d*|0)?(?:[.]\\d+)?$

to check it out. It works as expected. now I want to add a user-defined string to the regular expression so that its value does not change. is there any way?

Answer 1

, , , , , .

, alternation:

"^(?:(?:[1-9]\\d*|0)?(?:[.]\\d+)?|MY STRING)?$"
  ^^^                            ^^^^^^^^^^^^

​​- regex

:

• ^ -
• (?: - ,
  • (?:[1-9]\d*|0)?(?:[.]\d+)? -
  • | -
  • MY STRING - MY STRING
• )? - (- ?)
• $ -

MY STRING - , , , escaping regex ( Java Pattern.quote(user_str))..