Pattern Matching and Grouping

[aru211285]

i need to extract the number part from the string which looks like "(7 r 8digits).txt". i need to store this found string in some variable, but i am confused wih the groups twhether o get the string as group() or group(1).

Pattern p = Pattern.compile("\b[0-9]{7,8}\b");
Matcher matcher = p.matcher("num"); //where num looks like10986745.txt r 0986745.txt
String identifier = matcher.group();
System.out.println(identifier);

But i am getting the output as no match found.
So it would be very helpful if some one would clear this

[Lensva]

provided the example you gave is normal and not just to illustrate the problem, couldnt you simply use:

String a = "1234567.txt";
Pattern b= Pattern.compile("\\.");
System.out.println(b.split(a)[0]);

[aru211285]

Thank you very much for the reply. It worked but im curious to know how can we do this with grouping.....so that i can handle complex regular expressions ....

[Ezzaral]

Use

Pattern.compile("(\\d{7,8}).txt");

and retrieve it with group(1).