Question

Pattern p = Pattern.compile("(ma)|([a-zA-Z_]+)");
Matcher m = p.matcher("ma");
m.find();
System.out.println("1 " + m.group(1) + ""); //ma
System.out.println("2 " + m.group(2)); // null
Matcher m = p.matcher("mad");
m.find();
System.out.println("1 " + m.group(1) + ""); //ma
System.out.println("2 " + m.group(2)); // null

But I need that the string “mad” would be in the 2nd group.

Answer 1

I think what you are looking for is something like:

(ma(?!d))|([a-zA-Z_]+)

from “perldoc perlre”:

“(?!pattern)”
A zero-width negative look-ahead assertion. For
example
“/foo(?!bar)/” matches any occurrence of “foo” that
isn’t
followed by “bar”.

the only thing I’m not sure about is whether Java supports this syntax, but I think it does.