Java Regex: Extracting info from string to variables

Question

I'm extracting three parts of a string with regex in Java and the following working code. I'm relatively new in regex and I'm feeling a bit silly using several expressions for such a simple search and extraction.

Can anyone of you help me with a more elegant and simple solution? I need the data to be stored in three seperate variables as the code suggests.

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

public class Test {

    public static void main(String[] args) {

        String input = "lat: 56.894205 long: 008.528896 speed: 000.0 24/02/13 21:21   bat:F signal:F  imei:12345678901";

        String lat = regexSearch("(?<=lat: )\\d+.\\d+", input);
        String lng = regexSearch("(?<=long: )\\d+.\\d+", input);
        String imei = regexSearch("(?<=imei:)\\d+", input);

        if (lat != null && lng != null && imei != null) {
            System.out.println(lat);
            System.out.println(lng);
            System.out.println(imei);
        }
    }

    public static String regexSearch(String regex, String input) {
        Matcher m = Pattern.compile(regex).matcher(input);
        if (m.find()) return m.group();
        return null;
    }

}

Output:

56.894205
008.528896
12345678901

Edit: I need the code to handle varying length of the "lat" and "long" data (e.g. 56.89405 and 56.894059 etc.)

In your place, I would work with substring, indexOf("lat: ") and so on to avoid three compiled regular expressions. — Smutje
– Smutje, Commented Jan 22, 2015 at 13:27
@TheLostMind: As my edit suggests, the string will be of varying length, e.g. more digits in the lat and long info. — user2543930
– user2543930, Commented Jan 22, 2015 at 13:34
@SimonGregersen - If the format / pattern of the String will remain the same, then you might look at my solution — TheLostMind
– TheLostMind, Commented Jan 22, 2015 at 13:35

hwnd · Accepted Answer · 2015-01-22 14:28:28Z

4

You could use Named Capturing Groups to separate the match groups and then assign each match group to a string variable of your choice. Below is a working example you can go off of ...

String s  = "lat: 56.894205 long: 008.528896 speed: 000.0 24/02/13 21:21   bat:F signal:F  imei:12345678901";
Pattern p = Pattern.compile("lat: (?<lat>\\d+\\.\\d+) long: (?<lng>\\d+\\.\\d+).*imei:(?<imei>\\d+)");
Matcher m = p.matcher(s);
while (m.find()) {
    String lat  = m.group("lat");
    String lng  = m.group("lng");
    String imei = m.group("imei");
    System.out.println(lat);  //=> "56.894205"
    System.out.println(lng);  //=> "008.528896"
    System.out.println(imei); //=> "12345678901"
}

edited Jan 22, 2015 at 14:28

answered Jan 22, 2015 at 14:21

hwnd

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Comments

Stephan · Accepted Answer · 2015-01-22 14:19:43Z

You can simplify the code like this:

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

public class Test {

    public static void main(String[] args) {

        String input = "lat: 56.894205 long: 008.528896 speed: 000.0 24/02/13 21:21   bat:F signal:F  imei:12345678901";

        Pattern p = Pattern.compile("lat:\\s+(?<latitude>\\d+\\.\\d+)\\s+long:\\s+(?<longitude>\\d+\\.\\d+)\\s+.+?imei:(?<imei>\\d+)");
        Matcher m = p.matcher(input);

        if (m.find()) {
            String lat = m.group("latitude");
            String lng = m.group("longitude");
            String imei = m.group("imei");

            System.out.println(lat);
            System.out.println(lng);
            System.out.println(imei);
        }
    }
}

Here I use one regex only for extracting the numbers. Compiling a pattern can be a costly thing.
I'm using named capturing groups ((?<latitude>...). It makes regex reading easier.
The value the named groups capture is retrieved with Matcher#group(String name)

TheLostMind · Accepted Answer · 2015-01-22 13:32:05Z

0

The term elegant is relative and varies from person to person. So, from my perspective, you can use a single regex like this :

public static void main(String[] args) {
    String input = "lat: 56.894205 long: 008.528896 speed: 000.0 24/02/13 21:21   bat:F signal:F  imei:12345678901";
    Pattern p = Pattern.compile("(\\d+\\.\\d+)(?!\\s\\d+)|(\\d+$)"); // negative lookahead to prevent matching of speed
    Matcher m = p.matcher(input);
    while (m.find()) {
        System.out.println(m.group());
    }

}

O/P :

56.894205
008.528896
12345678901

answered Jan 22, 2015 at 13:32

TheLostMind

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3 Comments

user2543930 Over a year ago

How do I extract the info in seperate variables then?

TheLostMind Over a year ago

@SimonGregersen - You could add them to a list and then get values from list . at pos 0, you will have lattitude, at pos1 you will have longitude and at pos 2 you will have imei number

TheLostMind Over a year ago

@AvinashRaj - Then this answer won't work.. He can use his regex or something else. He might actually use split then.

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