Java Regex expression not working

Question

I have a problem with not working REGEX. I dont know what I am doing wrong. My code:

String test = "timetable:xxxxxtimetable:;   timetable: fullihhghtO;";
Pattern p = Pattern.compile("\\btimetable:(.*);");
//also tried "timetable:(.*);" and "(\\btimetable:)(.*)(;)"
Matcher m = p.matcher(test);

while(m.find()) {
    System.out.println("S:" + m.start() + ", E:" + m.end());
    System.out.println("x: "+ test.substring(m.start(), m.end()));
}

Expected result:

(1) "timetable:xxxxxtimetable:"
(2) "timetable: fullihhghtO"

I thanks for any help.

Nir Alfasi · Accepted Answer · 2017-10-21 21:49:22Z

1

A non-capturing group could be handy in our case:

    String test = "timetable:xxxxxtimetable:;   timetable: fullihhghtO;";
    Pattern p = Pattern.compile("(?:\\btimetable:(.*?);)+"); // <-- here
    Matcher m = p.matcher(test);

    int i = 1;
    while (m.find()) {
        System.out.println(i + ") "+ m.group(1));
        i++;
    }

OUTPUT

1) xxxxxtimetable:
2)  fullihhghtO

Regex explained:
(?:\\btimetable:(.*?);)+ by using the non-capturing (?:\\btimetable:...) we'll consume the "timetable:" without capturing it, then the second matching group (.*?) captures what we want to capture (everything between \btimetable: and ;). Pay special attention to the non-greedy term: .*? which means that we'll consume the minimum possible amount of characters until the ;. If we won't use this lazy form, the regex will use "greedy" default mode and will consume all the characters until the last ; in the string!

Now, all that is relevant if you wanted to catch only the unique part, but if you wanted to catch the whole thing:

1) timetable:xxxxxtimetable:;
2) timetable: fullihhghtO;

It can be done easily by modifying the line with the regex to:

Pattern p = Pattern.compile("\\b(timetable:.*?;)+");

which is even simpler: only one capturing group (see that we still have to use the non-greedy mode!).

edited Oct 21, 2017 at 21:49

answered Oct 21, 2017 at 21:42

Nir Alfasi

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1 Comment

Noro96 Over a year ago

I cannot add you point, because I am low level, but I really thanks you for your time and for your help, first case is what I needed, but I wanted to do it somehow through test.split(":"), but you show me better solution thanks. You helped me a lot.

azro · Accepted Answer · 2017-10-21 21:32:01Z

0

You don't need to use regex, a simple split would do it :

public static void main(String[] args) throws IOException {
    String test = "timetable:xxxxxtimetable:;   timetable: fullihhghtO;";
    String[] array = test.split(";");
    String str1 = array[0].trim();
    String str2 = array[1].trim();

    System.out.println(str1 + "\n" + str2);      //timetable:xxxxxtimetable:
                                                 //timetable: fullihhghtO
}

answered Oct 21, 2017 at 21:32

azro

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