* The class FilterOutputStream itself simply overrides
* all methods of OutputStream with versions that pass
* all requests to the underlying output stream. Subclasses of
* FilterOutputStream may further override some of these
* methods as well as provide additional methods and fields.
*
* @author Jonathan Payne
* @since 1.0
*/
public class FilterOutputStream extends OutputStream {
/**
* The underlying output stream to be filtered.
*/
protected OutputStream out;
/**
* Whether the stream is closed; implicitly initialized to false.
*/
private volatile boolean closed;
/**
* Object used to prevent a race on the 'closed' instance variable.
*/
private final Object closeLock = new Object();
/**
* Creates an output stream filter built on top of the specified
* underlying output stream.
*
* @param out the underlying output stream to be assigned to
* the field {@code this.out} for later use, or
* null if this instance is to be
* created without an underlying stream.
*/
public FilterOutputStream(OutputStream out) {
if (out == null) {
throw new NullPointerException();
}
this.out = out;
}
/**
* Writes the specified byte to this output stream.
*
* The write method of FilterOutputStream
* calls the write method of its underlying output stream,
* that is, it performs {@code out.write(b)}.
*
* Implements the abstract {@code write} method of {@code OutputStream}.
*
* @param b the byte.
* @exception IOException if an I/O error occurs.
*/
@Override
public void write(int b) throws IOException {
out.write(b);
}
/**
* Writes b.length bytes to this output stream.
*
* The write method of FilterOutputStream
* calls its write method of three arguments with the
* arguments b, 0, and
* b.length.
*
* Note that this method does not call the one-argument
* write method of its underlying output stream with
* the single argument b.
*
* @param b the data to be written.
* @exception IOException if an I/O error occurs.
* @see java.io.FilterOutputStream#write(byte[], int, int)
*/
@Override
public void write(byte b[]) throws IOException {
write(b, 0, b.length);
}
/**
* Writes len bytes from the specified
* byte array starting at offset off to
* this output stream.
*
* The write method of FilterOutputStream
* calls the write method of one argument on each
* byte to output.
*
* Note that this method does not call the write method
* of its underlying output stream with the same arguments. Subclasses
* of FilterOutputStream should provide a more efficient
* implementation of this method.
*
* @param b the data.
* @param off the start offset in the data.
* @param len the number of bytes to write.
* @exception IOException if an I/O error occurs.
* @see java.io.FilterOutputStream#write(int)
*/
@Override
public void write(byte b[], int off, int len) throws IOException {
if ((off | len | (b.length - (len + off)) | (off + len)) < 0)
throw new IndexOutOfBoundsException();
for (int i = 0 ; i < len ; i++) {
write(b[off + i]);
}
}
/**
* Flushes this output stream and forces any buffered output bytes
* to be written out to the stream.
*
* The flush method of FilterOutputStream
* calls the flush method of its underlying output stream.
*
* @exception IOException if an I/O error occurs.
* @see java.io.FilterOutputStream#out
*/
@Override
public void flush() throws IOException {
out.flush();
}
/**
* Closes this output stream and releases any system resources
* associated with the stream.
*
* When not already closed, the {@code close} method of {@code * FilterOutputStream} calls its {@code flush} method, and then * calls the {@code close} method of its underlying output stream. * * @exception IOException if an I/O error occurs. * @see java.io.FilterOutputStream#flush() * @see java.io.FilterOutputStream#out */ @Override public void close() throws IOException { if (closed) { return; } synchronized (closeLock) { if (closed) { return; } closed = true; } Throwable flushException = null; try { flush(); } catch (Throwable e) { flushException = e; throw e; } finally { if (flushException == null) { out.close(); } else { try { out.close(); } catch (Throwable closeException) { // evaluate possible precedence of flushException over closeException if ((flushException instanceof ThreadDeath) && !(closeException instanceof ThreadDeath)) { flushException.addSuppressed(closeException); throw (ThreadDeath) flushException; } if (flushException != closeException) { closeException.addSuppressed(flushException); } throw closeException; } } } } }