Split a string by commas but no inside parenthesis

Question

Update: It's not duplicate with Regex to match only commas not in parentheses? because it matches commas in the string, but I want to split the string by commas and not to find the commas

My Test String

String myString = "x1, x2, x3,  x4, x1(x1, x2,x3,x4)";

My Desired Output

x1
x2
x3
x4
x1(x1, x2,x3,x4)

I've just read How do I split a string by commas except inside parenthesis, using a regular expression? answer, but when I try to get it to Java error occurs

I try this:

String[] parts = myString.split("((?:[^,(]+|(\((?>[^()]+|\g<-1>)*\)))+)");

Error: Illegal escape character in string literal

What should I do?