Recently in learning, regular expression said online articles, ordinary capturing packet when mixed with named capture groups, numbering rule is: regardless of named groups, only for the average capture group numbered, common group after the number of named groups continue to number,
But I have found in local test run results do not conform to the rules,

 String STR="2012-06-09"; 
The Pattern p=Pattern.com running (" (?  \ \ d {4}) - (\ \ d {2}) - (\ \ d {2}) "); 
The Matcher m=p. atcher (STR); 
If (m. ind ()) {
System. The out. Println (m.g roup (0)); 
System. The out. Println (m.g roup (1)); 
System. The out. Println (m.g roup (2)); 
System. The out. Println (m.g roup (3)); 
System. The out. Println (m.g roup (" year ")); 
} 
Results: 
Grouping 0:20 12-06-09 
Group 1:12 
Grouping 2:06 
Grouping 3:09 
Grouping year: 2012 

According to the online said the number of rules, group 1 should be output in 06, rather than the year 2012, year should be a group 3.
Which is a big help to explain, I write wrong or there is something wrong with the rules of online?