public TermVectorsWriter(Directory directory,
    String segment,
    FieldInfos fieldInfos) throws IOException 
{
      
    // Open files for TermVector storage
    tvx = directory.createOutput(segment + "." + IndexFileNames.VECTORS_INDEX_EXTENSION);
    tvx.writeInt(TermVectorsReader.FORMAT_VERSION);
    tvd = directory.createOutput(segment + "." + IndexFileNames.VECTORS_DOCUMENTS_EXTENSION);
    tvd.writeInt(TermVectorsReader.FORMAT_VERSION);
    tvf = directory.createOutput(segment + "." + IndexFileNames.VECTORS_FIELDS_EXTENSION);
    tvf.writeInt(TermVectorsReader.FORMAT_VERSION);
    this.fieldInfos = fieldInfos;
}

 public final  void addAllDocVectors(TermFreqVector[] vectors) throws IOException 
{
    tvx.writeLong(tvd.getFilePointer());
    if (vectors != null) {
      final int numFields = vectors.length;
      tvd.writeVInt(numFields);
      long[] fieldPointers = new long[numFields];
      for (int i=0; i< numFields; i++) {
        fieldPointers[i] = tvf.getFilePointer();
        final int fieldNumber = fieldInfos.fieldNumber(vectors[i].getField());
        // 1st pass: write field numbers to tvd
        tvd.writeVInt(fieldNumber);
        final int numTerms = vectors[i].size();
        tvf.writeVInt(numTerms);
        final TermPositionVector tpVector;
        final byte bits;
        final boolean storePositions;
        final boolean storeOffsets;
        if (vectors[i] instanceof TermPositionVector) {
          // May have positions & offsets
          tpVector = (TermPositionVector) vectors[i];
          storePositions = tpVector.size()  > 0 && tpVector.getTermPositions(0) != null;
          storeOffsets = tpVector.size()  > 0 && tpVector.getOffsets(0) != null;
          bits = (byte) ((storePositions ? TermVectorsReader.STORE_POSITIONS_WITH_TERMVECTOR : 0) +
                         (storeOffsets ? TermVectorsReader.STORE_OFFSET_WITH_TERMVECTOR : 0));
        } else {
          tpVector = null;
          bits = 0;
          storePositions = false;
          storeOffsets = false;
        }
        tvf.writeVInt(bits);
        final String[] terms = vectors[i].getTerms();
        final int[] freqs = vectors[i].getTermFrequencies();
        String lastTermText = "";
        for (int j=0; j< numTerms; j++) {
          final String termText = terms[j];
          int start = StringHelper.stringDifference(lastTermText, termText);
          int length = termText.length() - start;
          tvf.writeVInt(start);       // write shared prefix length
          tvf.writeVInt(length);        // write delta length
          tvf.writeChars(termText, start, length);  // write delta chars
          lastTermText = termText;
          final int termFreq = freqs[j];
          tvf.writeVInt(termFreq);
          if (storePositions) {
            final int[] positions = tpVector.getTermPositions(j);
            if (positions == null)
              throw new IllegalStateException("Trying to write positions that are null!");
            assert positions.length == termFreq;
            // use delta encoding for positions
            int lastPosition = 0;
            for(int k=0;k< positions.length;k++) {
              final int position = positions[k];
              tvf.writeVInt(position-lastPosition);
              lastPosition = position;
            }
          }
          if (storeOffsets) {
            final TermVectorOffsetInfo[] offsets = tpVector.getOffsets(j);
            if (offsets == null)
              throw new IllegalStateException("Trying to write offsets that are null!");
            assert offsets.length == termFreq;
            // use delta encoding for offsets
            int lastEndOffset = 0;
            for(int k=0;k< offsets.length;k++) {
              final int startOffset = offsets[k].getStartOffset();
              final int endOffset = offsets[k].getEndOffset();
              tvf.writeVInt(startOffset-lastEndOffset);
              tvf.writeVInt(endOffset-startOffset);
              lastEndOffset = endOffset;
            }
          }
        }
      }
      // 2nd pass: write field pointers to tvd
      long lastFieldPointer = 0;
      for (int i=0; i< numFields; i++) {
        final long fieldPointer = fieldPointers[i];
        tvd.writeVLong(fieldPointer-lastFieldPointer);
        lastFieldPointer = fieldPointer;
      }
    } else
      tvd.writeVInt(0);
}

Add a complete document specified by all its term vectors. If document has no term vectors, add value for tvx.

 final  void close() throws IOException 
{
    // make an effort to close all streams we can but remember and re-throw
    // the first exception encountered in this process
    IOException keep = null;
    if (tvx != null)
      try {
        tvx.close();
      } catch (IOException e) {
        if (keep == null) keep = e;
      }
    if (tvd != null)
      try {
        tvd.close();
      } catch (IOException e) {
        if (keep == null) keep = e;
      }
    if (tvf != null)
      try {
        tvf.close();
      } catch (IOException e) {
        if (keep == null) keep = e;
      }
    if (keep != null) throw (IOException) keep.fillInStackTrace();
}

Close all streams.