@Override
  public void writeDouble(double v) throws IOException {
    size += 8;
  }
Writes a <code>double</code> value, which is comprised of eight bytes, to the output stream. It
does this as if it first converts this <code>double</code> value to a <code>long</code> in
exactly the manner of the <code>Double.doubleToLongBits</code> method and then writes the
<code>long</code> value in exactly the manner of the <code>writeLong</code> method. The bytes
written by this method may be read by the <code>readDouble</code> method of interface
<code>DataInput</code>, which will then return a <code>double</code> equal to <code>v</code>.

@param v the <code>double</code> value to be written.
@exception IOException if an I/O error occurs.
geode-core/src/main/java/org/apache/geode/internal/NullDataOutputStream.java