code: public void writeBlock(byte[] block) throws IOException {
  
          if (block.length != 512) {
              throw new IllegalArgumentException(
                  RB.singleton.getString(RB.BAD_BLOCK_WRITE_LEN, block.length));
          }
  
          write(block, block.length);
      }
docs: Write a user-specified 512-byte block.
  
  For efficiency, write(int) should be used when writing file body content.
  
  @see #write(int)