text: public Builder Add(int docID){if (docID <= lastDocID){throw new System.ArgumentException("Doc ids must be added in-order, got " + docID + " which is <= lastDocID=" + lastDocID);}int wordNum = WordNum(docID);if (this.wordNum == -1){this.wordNum = wordNum;word = 1 << (docID & 0x07);}else if (wordNum == this.wordNum){word |= 1 << (docID & 0x07);}else{AddWord(this.wordNum, (byte)word);this.wordNum = wordNum;word = 1 << (docID & 0x07);}lastDocID = docID;return this;}