java - Getting the "context" text of a matched group -

i'm using matcher class of java strings, when matches, find begin index , end index. want x preceding , proceeding characters.

so did call substring method on string {begin index minusx} {end index plusx}, seems little heavy, every match, i'll have loop string it's context.

i wanted know whether there's better way that.

here i've done far: part bothers me text.substring, how expensive it

    string text = "some 22 text 44 characters";     matcher matcher = pattern.compile("\\d{2}").matcher(text);     int x = 5;     while (matcher.find()) {         string match = matcher.group();         int start = matcher.start();         int end = matcher.end();         string pretext = text.substring(start - x, start);         string postext = text.substring(end, end + x);         system.out.println(pretext + " - " + match + " - " + postext);     } 

suggested answer of using grouping solve this: using regex (.{5})(\d{2}(.{5}). first of all, wouldn't able captures ones without @ least 5 characters before it. solution (.{0,5})(\d{2})(.{0.5}), nice simple regex (\d{2})but 1 "c?at" , given text "cat" match groups

1. c
2. at
3.  

string text = "some 22 text 44 characters"; matcher matcher = pattern.compile("(.{5})(\\d{2})(.{5})").matcher(text);  while (matcher.find()) {     system.out.println(matcher.group(1) + " - " + matcher.group(2) + " - " + matcher.group(3)); } 

output :

some  - 22 -  text  - 44 -  char