How to use a regular expression and assign the result to variables in Android?

Question

I have a string named s_Result which will be parsed from the Internet. The format may be "Distance: 2.8km (about 9 mins)", and there are 4 variables which are f_Distance, m_DistanceUnit, f_timeEst, m_timeEstUnit.

My question is how to parse s_Result and assign 2.8, km, 9, mins into f_Distance, m_distanceUnit, f_timeEst and m_timeEstUnit respectively using regular expression?

I tried using "\d+(\.\d+)?" in RegEx Tester and the result showed 2 matches found, but if I use "\\d+(\\.\\d+)?" in Android code, it showed no matches!

Any suggestions what might be going wrong?

Answer 1

I tried using "\d+(\.\d+)?" in RegEx Tester and the result showed 2 matches found, but if I use "\\d+(\\.\\d+)?" in Android code, it showed no matches!

Probably you was using String#matches() or Matcher#matches() which would match on the entire string. The regex is then actually "^\\d+(\\.\\d+)?$". Better use Matcher#find() instead.

String s = "Distance: 2.8km (about 9 mins)";
Matcher m = Pattern.compile("\\d+(\\.\\d+)?").matcher(s);
while (m.find()) {
    System.out.println(m.group(0)); // 2.8 and 9
}

That said, have you considered writing a parser?

Answer 2

Something like that?

String s_Result="Distance: 2.8km (about 9 mins)";

//Distance parsing
Pattern p = Pattern.compile("Distance: (\\d+(\\.\\d+)?)(.*?)\\b");
Matcher m = p.matcher(s_Result);
if(m.find()){
    MatchResult mr=m.toMatchResult();
    f_Distance=mr.group(1);//2.8
    m_DistanceUnit=mr.group(3);//km
}

//Time parsing
p = Pattern.compile("about (\\d+(\\.\\d+)?) (.*)\\b");
m = p.matcher(s_Result);
if(m.find()){
    MatchResult mr=m.toMatchResult();
    f_timeEst=mr.group(1);//9
    m_timeEstUnit=mr.group(3);//min
}

And here's another option for you, to match more flexible format:

String s_Result="Distance: 2.8km (about 9 mins)";
Pattern p = Pattern.compile("(\\d+(\\.\\d+)?) ?(\\w+?)\\b");
Matcher m = p.matcher(s_Result);
while(m.find()){
    MatchResult mr=m.toMatchResult();
    String value=mr.group(1);//2.8 and 9 come here
    String units=mr.group(3);//km and mins come here
}

Answer 3

It's absolutely the same as in Java.

Really, most of Android questions are not related to Android itself, but to Java programming in general. Please try to search for more general questions before posting new 'Android' questions.