Java (String Variable).replaceAll() argument \\D with exceptions?

Question

I'd like to read through a user input string that removes all nondigit characters excluding some characters like +,-,/,. etc. This is for a calculator. Is there an easy way to do this or do I need to split the initial string beforehand.

Answer 1

You can use this. Add any characters you want to keep inside the [ ]

string.replaceAll("[^0-9+-]", "");

When you use ^ inside [] , it will match any character that is NOT in [] (excluding the ^ ).

In this case, it will match any character that is not a number (from 0 to 9), not a + , and not a - .