public void inSertIntoPostingMap(String word,Integer docId,int contextWeight){
		TreeMap<Integer, Integer> termFreqMap=postingMap.get(word); // find the termDocMap for the give map;	
		if(termFreqMap==null){    // the word is first time occurs;
			termFreqMap=new TreeMap<Integer,Integer>();
			termFreqMap.put(docId,contextWeight); // put the doc ID and context into termDocMap;
			postingMap.put(word, termFreqMap);
		}else{   // there is a mapping for this word;
			Integer freq=termFreqMap.get(docId);// the freq mapped from the given docId;
			if (freq==null){  // the Docment ID with the given word was not inserted before
				termFreqMap.put(docId,contextWeight); // put the doc ID into termFreqMap;
				postingMap.put(word, termFreqMap);
//				inSertIntoLexMap(word);// update the lexicon map by this word;
			}else{// document ID was existed in the map of the given word;
				freq+=contextWeight; // increment the term frequency of the given word in the docId;
				if(freq>255) {freq=255;}
				termFreqMap.put(docId,freq);
				postingMap.put(word, termFreqMap);
			}
		}
	}