try{
  Mongo mongo = new Mongo("localhost");
  DB db = mongo.getDB("test");
  GridFS gridFS = new GridFS(DB, "file");
  File file = new File("d:/logs.txt");  // the file's size is about 200 byte.
  GridFSInputFile input = gridFS.createFile(file);
  input.save():
  GridFSDBFile read = gridFS.find(new ObjectId(input.getId().toString()));
  try{
  }catch(IOException e){
    System.out.println(e.toString()); // here catch the exception: com.mongodb.MongoException: can't find a chunk! file id.....
  }
}catch(Exception e){
 System.out.println(e.toString());
}

public long skip(long numBytesToSkip) throws IOException { 
            if (numBytesToSkip <= 0) 
                return 0; 


            if (_currentChunkIdx == _numChunks) 
                //We're actually skipping over the back end of the 
file, short-circuit here 
                //Don't count those extra bytes to skip in with the 
return value 
                return 0; 


            if (_offset + numBytesToSkip <= _chunkSize) { 
                //We're skipping over bytes in the current chunk, 
adjust the offset accordingly 
                _offset += numBytesToSkip; 
                if (_data == null && _currentChunkIdx < _numChunks) // 
if the _currentChunkIdx is -1, getChunk will throw exception 
                    _data = getChunk(_currentChunkIdx); 


                return numBytesToSkip; 
            } 


            //We skipping over the remainder of this chunk, could do 
this less recursively... 
            ++_currentChunkIdx; 
            long skippedBytes = 0; 
            if (_currentChunkIdx < _numChunks) 
                skippedBytes = _chunkSize - _offset; 
            else 
                skippedBytes = _lastChunkSize; 


            _offset = 0; 
            _data = null; 


            return skippedBytes + skip(numBytesToSkip - skippedBytes); 
        }