Question

I am using java for my program
suppose i have a string such as this

xx(yyzz(iijj))qq((kkll)(gghh))

Is there any way in which i could match xx(yyzz(iijj)) and qq((kkll)(gghh)) separately using a regex?

Answer 1

You can match nested parenthesis using regex up to a fixed level. But more than 2 level will become rather messy (2 already is, to be frank). This will match your examples:

\(([^()]*+|\([^()]*+\))*\)

A quick explanation:

\(              # match a '(' 
(               # open group 1
  [^()]*+       #   match any chars other than '(' and ')'
  |             #   OR
  \([^()]*+\)   #   match '(...)'
)*              # close group 1 and repeat it zero or more times
\)              # match a '(' 

See the demo on ideone.com

There are regex flavors that can match an arbitrary number of nesting (Perl, .NET, PHP), but Java is not one of them.

But looking at the comment you posted under your question, I’d not handle this with regex, but a proper parser (be it a handcrafted one, or a generated).