正则表达式中的多个条件

Question

I want to replace my variable name in text file using regular expression with following condition : let's take example that I want to replace log with LOG

1. If the line starts with import then I don't want to replace it. like import com.test.log.myfile; distance between import and log can be max up to 1000 → I don't want to replace here
2. If it is contained within double quotes such as "log" then I don't want to replace it.

3. Other than above 2 condition, I want to change it everywhere like this:

    log="log" ; // should be LOG="log"; log.test(); // should be LOG.test(); 

I used below regular expression but it fulfilling my second and third condition but not first one: Link

(\blog\b)(?=(?:[^\"]|[\"][^\"]*[\"])*$)

can someone please help me to how to proceed or fix it ?

Answer 1

You can use lookarounds to determine if it is surrounded by quotes.

Like this (?<!")log(?!")

or if lookarounds aren't supported in whatever language you're using,

You can use this (?:[^"]|^)(log)(?:[^"]|$)

Keep in mind if you use the 2nd one, you'll want to replace capture group 1, not the whole match. As you can see in my example it cuts the letter (or newline) before and after "log" if you use the full match.

Answer 2

Given your current requirements and restrictions, you may use the following Java regex compliant pattern:

s.replaceAll("(?<!^import\\b.{0,1000})\\b(log)\\b(?=(?:[^\"]|\"[^\"]*[\"])*$)", "LOG")

See the Java demo here .

Details

• (?<!^import\\\\b.{0,1000}) - a negative lookbehind that fails the match if the current location is preceded with import and any 0 to 1000 symbols other than line break chars at the start of the string (or line if Pattern.MULTILINE flag is used)
• \\\\b(log)\\\\b - Group 1: log whole word
• (?=(?:[^\\"]|\\"[^\\"]*[\\"])*$) - there should be no " chars or there may be any number of substrings inside two quotes right after log .