regex to find parenthesis and the numbers within. Java -

what regex used find parenthesis , numbers within these paernthesis?

desired output:

• input = "hello (1) world".replaceall(regex, "*");
• result = hello * world

i tried following:

• input = "hello (1) world".replaceall("([0-9])", "*");
• result = ""hello (*) world"

why?

( , ) reserved characters in regexes (they create group). need escape them replace them:

"hello (1) world".replaceall("\\([0-9]\\)", "*");