java regular expression with replaceAll on string

Question

I have two strings :

s = "aaaaaaa" and m = "a"

I want output as commonChars="a" but i am getting commonChars="aaaaaaa" and for s = "a" m = "aaaa"

I want output commonChars="a"

Can anyone suggest me regular expression for that ?

My code is

String commonChars = s.replaceAll("[^" + m + "]", "");

Answer 1

You could do

String commonChars = s.replaceAll(m + "+", m);

• Jayesh Ahir: Thank you..but what if i also want to find the common character in two string like if s = "avfd" m = "av" than output is commonChars="av"
• Prasad: @JayeshAhir It depends on how you use it. :)
• Jayesh Ahir: Basicly i want find common characters in two string ..so can you suggest me regex for that..thanks
• tilois: You can't use regular expressions that way. A regular expression is a single expression which matches a number of strings. It can't be used to extract common characters of multiple strings.
• Reimeus: Indeed see this post to see how problematic that can be