question: public static String formatTimeDelta ( long time , CharSequence sep ) { final StringBuilder sb = new StringBuilder ( ) ; final Formatter fmt = new Formatter ( sb ) ; for ( int i = TIME_UNIT_SIZES . length - 1 ; i >= 0 ; -- i ) { if ( i == 0 && sb . length ( ) > 4 ) { continue ; } if ( sb . length ( ) > 0 ) { sb . append ( sep ) ; } final long acValue = time / TIME_UNIT_SIZES [ i ] ; time = time % TIME_UNIT_SIZES [ i ] ; if ( ! ( acValue == 0 && sb . length ( ) == 0 ) ) { fmt . format ( "%0" + TIME_UNIT_DIGITS [ i ] + "d%s" , Long . valueOf ( acValue ) , TIME_UNIT_NAMES [ i ] ) ; } } fmt . close ( ) ; return sb . toString ( ) ; }
target:  Formats a time delta in human readable format.