Patten的group方法

获取括号中匹配到的第几组数据。例如

//mongodb://username:password@hostname:port/dbname
String  patternStr="mongodb://(.*),(.*):(.*)/(.*)"


Pattern pattern = Pattern.compile(patternStr);

pattern.matcher("mongodb://username:password@hostname:port/dbname")
m.find();
String user = m.group(1);
String ip= m.group(2);
String port= m.group(3);
String dbName= m.group(4);