Creates a <code>BufferedInputStream</code>
with the specified buffer size,
and saves its argument, the input stream
<code>inputStream</code>, for later use. An internal
buffer array of length <code>size</code>
is created and stored in <code>buf</code>.
@param inputStream the underlying input stream.
@param size the buffer size.
@exception IllegalArgumentException if {@code size <= 0}.
Creates a <code>BufferedInputStream</code> with the specified buffer size, and saves its argument, the input stream <code>inputStream</code>, for later use. An internal buffer array of length <code>size</code> is created and stored in <code>buf</code>.
@param inputStream the underlying input stream. @param size the buffer size. @exception IllegalArgumentException if {@code size <= 0}.