code: public BlockInfo[] getParityBlocks(BlockInfo[] blocks) {
      int numBlocks = (blocks.length / numStripeBlocks) * numParityBlocks
          + ((blocks.length % numStripeBlocks == 0) ? 0 : numParityBlocks);
      BlockInfo[] parityBlocks = new BlockInfo[numBlocks];
      int pos = 0;
      int parityEnd = numParityBlocks;
      for (int i = 0; i < numBlocks; i++) {
        parityBlocks[i] = blocks[pos];
        pos++;
        if (pos == parityEnd) {
          pos += numDataBlocks;
          parityEnd += numStripeBlocks;
        }
      }
      return parityBlocks;
    }
docs: Return only the parity blocks of the raided file