code: public static TimeBasedKeys create( int bitsUsedInCounter ) {
          CheckArg.isPositive(bitsUsedInCounter, "bitsUsedInCounter");
          int maxAvailableBitsToShift = Long.numberOfLeadingZeros(System.currentTimeMillis());
          CheckArg.isLessThan(bitsUsedInCounter, maxAvailableBitsToShift, "bitsUsedInCounter");
          return new TimeBasedKeys((short)bitsUsedInCounter);
      }
docs: Create a new generator that uses the specified number of bits for the counter portion of the keys.
  
  @param bitsUsedInCounter the number of bits in the counter portion of the keys; must be a positive number for which theere
  is enough space to left shift without overflowing.
  @return the generator instance; never null