Question

What I have wrong? When I set variable param=”MOON” I need get 333#444 but I’m getting: 333#444:JUPITER=555. So I just need one value at a time.

final String parameters = "WORLD=111#222:MOON=333#444:JUPITER=555:SATURN=666:";
final String param = "MOON";

Pattern pattern = Pattern.compile("(.*)(" + param + ")=(.*)(:+)(.*)");
Matcher matcher = pattern.matcher(parameters);

if(matcher.matches()) {
    System.out.println("3: " + matcher.group(3)); // Value that I needed: 333#444
}

Thank you.

Answer 1

I’m not totally sure, but maybe what you want is extract all key=value fields? If that is the case you should split your string at the : character and process all parts by themselves. Then match those string parts with the regular expression ([^=]+)=(.*) or, better, simply split each part at the = character. In this case you won’t even need regular expressions and possibly save program execution time! It’s easy to find the MOON= ... expression by search for MOON.

EDIT: I did the following old Java style test program (most probably can be improved):

class Test
{
        public static void main(String argv[])
        {
                String parameter="WORLD=111#222:MOON=333#444:JUPITER=555:SATURN=666";
                String[] elements=parameter.split(":");
                for (int i=0; i < elements.length; i++) {
                        String[] parts=elements[i].split("=", 2);
                        if ((parts.length == 2) && (parts[0].equals("MOON"))) {
                                System.out.println("MOON is "+parts[1]);
                        }
                }
        }
};

Output:

MOON is 333#444

In many cases using a regular expression is overkill, it can often be avoided and you save execution time. If you have a very long string you might just search for MOON and from there for the next : or end-of-string and then use split, but I would maybe use a regular expression in this case. It all depends if you need the other fields as well or not.