code: public long getIPv4PrefixCount(int prefixLength) {
  		if(prefixLength < 0) {
  			throw new PrefixLenException(this, prefixLength);
  		}
  		int bitCount = getBitCount();
  		if(bitCount <= prefixLength) {
  			return getIPv4Count();
  		}
  		int shiftAdjustment = bitCount - prefixLength;
  		long upperAdjusted = getUpper().longValue() >>> shiftAdjustment;
  		long lowerAdjusted = getLower().longValue() >>> shiftAdjustment;
  		return upperAdjusted - lowerAdjusted + 1;
  	}
docs: Equivalent to {@link #getPrefixCount(int)} but returns a long
  
  @return