Flushes this output stream and forces any buffered output bytes
to be written out. The general contract of <code>flush</code> is
that calling it is an indication that, if any bytes previously
written have been buffered by the implementation of the output
stream, such bytes should immediately be written to their
intended destination.
<p>
If the intended destination of this stream is an abstraction provided by
the underlying operating system, for example a file, then flushing the
stream guarantees only that bytes previously written to the stream are
passed to the operating system for writing; it does not guarantee that
they are actually written to a physical device such as a disk drive.
<p>
The <code>flush</code> method of <code>OutputStream</code> does nothing.
Flushes this output stream and forces any buffered output bytes to be written out. The general contract of <code>flush</code> is that calling it is an indication that, if any bytes previously written have been buffered by the implementation of the output stream, such bytes should immediately be written to their intended destination. <p> If the intended destination of this stream is an abstraction provided by the underlying operating system, for example a file, then flushing the stream guarantees only that bytes previously written to the stream are passed to the operating system for writing; it does not guarantee that they are actually written to a physical device such as a disk drive. <p> The <code>flush</code> method of <code>OutputStream</code> does nothing.
@exception IOException if an I/O error occurs.