使用Pattern Java中的正则表达式

Question

I have a string as below.

$Alarm:com.Alarm(a  ==  123 || (count  ==  12345 , time  matches  "24"))

whenever i encounter the above string i need to generate the following string.I mean i need to append the string "from Stream" as below.

$Alarm:com.Alarm(a  ==  123 || (count  ==  12345 , time  matches  "24")) from Stream.

I am currently using the following pattern to acheive the same in java.

Pattern eventPattern = Pattern.compile(".*?\\.Alarm\\(.*?\\)");

But i am getting the following output.

$Alarm:com.Alarm(a  ==  123 || (count  ==  12345 , time  matches  "24") from Stream )

Please provide me some pointers to acheive the correct output.The regular expression should consider only the last paranthesis.

Answer 1

You need to include parens matching in your Pattern. Something like the following:

Pattern eventPattern = Pattern.compile(".*?\\.Alarm\\(([^\\(]*?|\\([^\\)]*?\\))*\\)");

Things up to and including the first open parens: .*?\\\\.Alarm\\\\(

Stuff outside any internal parens: [^\\\\(]*?

Internal parens pair: \\\\([^\\\\)]*?\\\\)

Match any number of stuff outside parens or within a parens pair: ([^\\\\(]*?|\\\\([^\\\\)]*?\\\\))*

This RegexPlanet site is a great place to play with regexes to see what will work.