@Override
  public final double readDouble() throws IOException {
    return Double.longBitsToDouble(readLong());
  }
Reads a 64-bit <code>double</code> value from this stream.

@return the next <code>double</code> value from the source stream.

@throws IOException
          If a problem occurs reading from this DataInputStream.
ql/src/java/org/apache/hadoop/hive/ql/io/NonSyncDataInputBuffer.java