How can I strip all non digits in a string except the first character?

Question

I have a string that I want to make sure that the format is always a + followed by digits.
The following would work:

String parsed = input         


        

Answer 1

try this

1- This will allow negative and positive number and will match app special char except - and + at first position.

(?!^[-+])[^0-9.]

2- If you only want to allow + at first position

(?!^[+])[^0-9.]