java - Replace a substring in a string except when the string is inside quotes -

regex dialect: java
problem: given string, replace occurrences of substring inside it, except when these occurrences inside quotes.

example1:

string: "test substr 'test substr' substr" substring: "substr" replacement: "yyyy" output: "test yyyy 'test substr' yyyy" 

example2:

string: "test sstr 'test sstr' sstr" substring: "substr" replacement: "yyyy" output: "test sstr 'test sstr' sstr" 

example3:

string: "test 'test substr'" substring: "substr" replacement: "yyyy" output: "test 'test substr'" 

this best try far:

regex: ((?:[^']*'[^']+')*?[^']*?)substring replace: $1replacement 

the problem needs substring outside quotes after last string within quotes otherwise doesn't work, example3 fail (output: "test 'test yyyy'").

many help.

here's way:

public class main {     public static void main(string [] args) {          string[] tests = {                 "test substr 'test substr' substr",                 "test sstr 'test sstr' sstr",                 "test 'test substr'"         };          string regex = "substr(?=([^']*'[^']*')*[^']*$)";          for(string t : tests) {             system.out.println(t.replaceall(regex, "yyyy"));         }     } } 

prints:

 test yyyy 'test substr' yyyy test sstr 'test sstr' sstr test 'test substr' 

note not work if ' can escaped \ example.

a quick explanation:

the following: ([^']*'[^']*')* match 0 or number of single quotes non quotes in between, , [^']*$ matches non-quotes , end-of-string.

so, complete regex substr(?=([^']*'[^']*')*[^']*$) matches "substr" has 0 or number of single quotes ahead of it, when looking way end-of-string!

looking way end-of-string key here. if wouldn't that, following "substr" replaced:

aaa 'substr' bbb 'ccc ddd' eee            ^     ^       ^            |     |       |                ii     iii 

because "sees" number of single quotes ahead of (i , ii). must force @ entire string right of (all way $)!