Split string with only first instance java

Question

I have the below response from some telnet server

String response = "I:BARCO@noiclt22815||K:CMS||O:REgetPerspectiveList||A0:googleP||A1:yahooP||A2:gmail||A3:test||A4:hello||A16:CCTV Barco||A17:CCTV: Corridor CC||A18:CCTV: DR Andy Warhol||A19:CCTV: DR Gaudi (Analog)||A20:CCTV: DR Miro||A21:CCTV: Entrance CC||A22:CCTV: Gaudi Demo Room Megapixel||";

I want to get the attributes value for e.g A0, A1 etc and therefore I write the below logic

String[] strings = response.split("[||]");
List<String> list = new ArrayList<>();

for (String string : strings) {
    if (string.contains(":")) {
        String[] attributes = string.split(":");
        if (attributes[0].startsWith("A")) {
            list.add(attributes[1]);
        }
    }
}

But my problem is that string.split(":") split gives me string array but I requires only two length size string array only. For e.g. response A17 attribute gives me "CCTV" as attributes[1] and "Corridor CC" as attributes[2] but I requires "CCTV: Corridor CC" as attribute [1] only.

What regular expression I should write in string.split(regexp) so that string can be split based on first instance of colon operator only with exactly two length size string array.

You can use substring methods with indexOf to get the index of the first `:` and use substring till that index and put the two strings in array. — Tushar, Jan 21 '16 at 04:55
Pranav, it gives me same response as before means CCTV only for a17 attribute — ashishgupta_mca, Jan 21 '16 at 04:59
[*Some people, when confronted with a problem, think “I know, I'll use regular expressions.” Now they have two problems.* -- Jamie Zawinski](http://regex.info/blog/2006-09-15/247) — , Jan 21 '16 at 04:59
*"If you can do something without a regular expression, that is probably the better way to do it"* — , Jan 21 '16 at 05:01

score 1 · Answer 1 · answered Jan 21 '16 at 05:03

Set a limit on your split.

String[] attributes = string.split(":", 2);

This will force the regex to only be applied once (per the documentation it's applied n-1 times), so your groupings will only split on the colon character one time.

Once applied into the code, the result is as follows:

[googleP, yahooP, gmail, test, hello, CCTV Barco, CCTV: Corridor CC, CCTV: DR Andy Warhol, CCTV: DR Gaudi (Analog), CCTV: DR Miro, CCTV: Entrance CC, CCTV: Gaudi Demo Room Megapixel]

score 1 · Accepted Answer · answered Jan 21 '16 at 05:04

The code below splits on pipes first, and then uses a regex to extract out the properties and attributes. Note that even there, you could probably get away with doing another split.

String response = "I:BARCO@noiclt22815||K:CMS||O:REgetPerspectiveList||A0:googleP||A1:yahooP||A2:gmail||A3:test||A4:hello||A16:CCTV Barco||A17:CCTV: Corridor CC||A18:CCTV: DR Andy Warhol||A19:CCTV: DR Gaudi (Analog)||A20:CCTV: DR Miro||A21:CCTV: Entrance CC||A22:CCTV: Gaudi Demo Room Megapixel||";
String[] metaParts = response.split("\\|\\|");

for (int i=0; i < metaParts.length; ++i) {
    String property = metaParts[i].replaceAll("(.*):(.*)", "$1");
    String attribute = metaParts[i].replaceAll("(.*):(.*)", "$2");
    System.out.println(property + ":" + attribute);
}

As others here have said, regular expressions are not a panacea to cure all your development problems. And splitting is definitely doing the heavy lifting for this problem.

It really feels like this is a lot of work to accomplish something that regex perhaps really *shouldn't* be accomplishing... — Makoto, Jan 21 '16 at 05:10

Mohd Yunus · Answer 3 · 2016-01-21T05:39:58.940

import java.util.HashMap;
import java.util.regex.Matcher;
import java.util.regex.Pattern;

public class TestRegex {

public static void main(String[] args) {

    String response = "I:BARCO@noiclt22815||K:CMS||O:REgetPerspectiveList||A0:googleP||A1:yahooP||A2:gmail||A3:test||A4:hello||A16:CCTV Barco||A17:CCTV: Corridor CC||A18:CCTV: DR Andy Warhol||A19:CCTV: DR Gaudi (Analog)||A20:CCTV: DR Miro||A21:CCTV: Entrance CC||A22:CCTV: Gaudi Demo Room Megapixel||";
    Matcher mat = Pattern.compile("([^\\:]+)\\:([^\\|]+)\\|\\|").matcher(response);
    HashMap<String, String> hm = new HashMap();
    while( mat.find() ) {
        if(mat.groupCount() > 0) {
            String k = response.substring( mat.start(1), mat.end(1));
            String v = response.substring( mat.start(2), mat.end(2));
            hm.put(k, v);

            System.out.println(k +  " => " + v);   // debug
        }
    }
    // you may refer to your data from hashmap hm here!
    System.out.println(hm.get("K"));
}

} // end class

Split string with only first instance java

3 Answers3