Formatter Argument Index « Development « Java Tutorial

6.11.Formatter Argument Index
6.11.1.Using an Argument Index
6.11.2.Argument indexes enable you to reuse an argument without having to specify it twice
6.11.3.Relative index enables you to reuse the argument matched by the preceding format specifier
6.11.4.Relative indexes are especially useful when creating custom time and date formats