question: public Formatter format ( Locale l , String format , Object ... args ) { ensureOpen ( ) ; int last = - 1 ; int lasto = - 1 ; FormatString [ ] fsa = parse ( format ) ; for ( int i = 0 ; i < fsa . length ; i ++ ) { FormatString fs = fsa [ i ] ; int index = fs . index ( ) ; try { switch ( index ) { case - 2 : fs . print ( null , l ) ; break ; case - 1 : if ( last < 0 || ( args != null && last > args . length - 1 ) ) throw new MissingFormatArgumentException ( fs . toString ( ) ) ; fs . print ( ( args == null ? null : args [ last ] ) , l ) ; break ; case 0 : lasto ++ ; last = lasto ; if ( args != null && lasto > args . length - 1 ) throw new MissingFormatArgumentException ( fs . toString ( ) ) ; fs . print ( ( args == null ? null : args [ lasto ] ) , l ) ; break ; default : last = index - 1 ; if ( args != null && last > args . length - 1 ) throw new MissingFormatArgumentException ( fs . toString ( ) ) ; fs . print ( ( args == null ? null : args [ last ] ) , l ) ; break ; } } catch ( IOException x ) { lastException = x ; } } return this ; }
target:  Writes a formatted string to this object's destination using the specified locale, format string, and arguments.