question: public static StringBuilder formatTo ( StringBuilder buf , float [ ] d , String sep ) { if ( d == null ) { return buf . append ( "null" ) ; } if ( d . length == 0 ) { return buf ; } buf . append ( d [ 0 ] ) ; for ( int i = 1 ; i < d . length ; i ++ ) { buf . append ( sep ) ; buf . append ( d [ i ] ) ; } return buf ; }
target:  Formats the float array d with the default number format.