docs: public final String toHexString() {
  		if (this.hexString == null) {
  			final byte[] ba = new byte[SIZE];
  			longToByteArray(this.lowerPart, ba, 0);
  			longToByteArray(this.upperPart, ba, SIZE_OF_LONG);
  
  			this.hexString = StringUtils.byteToHexString(ba);
  		}
  
  		return this.hexString;
  	}