Storing backreferences from regex expression for later use

Question

If I have,

String str = "11"; 
Pattern p = Pattern.compile("(\\d)\\1"); 
Matcher m = p.matcher(str); 

How do I store use the result of \1 later? For example I want to do,

String str = "123123"; 
Pattern p = Pattern.compile("(\\d)\\1"); 
Matcher m = p.matcher(str);
String dependantString = //make this whatever was in group 1 of the pattern.

Is that possible?

Answer 1

You need to first call Matcher#find and then Matcher#group(1) like this:

String str = "123123"; 
Pattern p = Pattern.compile("(\\d+)\\1"); 
Matcher m = p.matcher(str);
if (m.find())
    System.out.println( m.group(1) ); // 123

PS: Your regex also needed some correction to use \\d+ instead of \\d.