* Applications that need to define a subclass of
* OutputStream must always provide at least a method
* that writes one byte of output.
*
* @author Arthur van Hoff
* @see java.io.BufferedOutputStream
* @see java.io.ByteArrayOutputStream
* @see java.io.DataOutputStream
* @see java.io.FilterOutputStream
* @see java.io.InputStream
* @see java.io.OutputStream#write(int)
* @since 1.0
*/
public abstract class OutputStream implements Closeable, Flushable {
/**
* Returns a new {@code OutputStream} which discards all bytes. The
* returned stream is initially open. The stream is closed by calling
* the {@code close()} method. Subsequent calls to {@code close()} have
* no effect.
*
*
While the stream is open, the {@code write(int)}, {@code * write(byte[])}, and {@code write(byte[], int, int)} methods do nothing. * After the stream has been closed, these methods all throw {@code * IOException}. * *
The {@code flush()} method does nothing.
*
* @return an {@code OutputStream} which discards all bytes
*
* @since 11
*/
public static OutputStream nullOutputStream() {
return new OutputStream() {
private volatile boolean closed;
private void ensureOpen() throws IOException {
if (closed) {
throw new IOException("Stream closed");
}
}
@Override
public void write(int b) throws IOException {
ensureOpen();
}
@Override
public void write(byte b[], int off, int len) throws IOException {
Objects.checkFromIndexSize(off, len, b.length);
ensureOpen();
}
@Override
public void close() {
closed = true;
}
};
}
/**
* Writes the specified byte to this output stream. The general
* contract for write is that one byte is written
* to the output stream. The byte to be written is the eight
* low-order bits of the argument b. The 24
* high-order bits of b are ignored.
*
* Subclasses of OutputStream must provide an
* implementation for this method.
*
* @param b the byte.
* @exception IOException if an I/O error occurs. In particular,
* an IOException may be thrown if the
* output stream has been closed.
*/
public abstract void write(int b) throws IOException;
/**
* Writes b.length bytes from the specified byte array
* to this output stream. The general contract for write(b)
* is that it should have exactly the same effect as the call
* write(b, 0, b.length).
*
* @param b the data.
* @exception IOException if an I/O error occurs.
* @see java.io.OutputStream#write(byte[], int, int)
*/
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 general contract for write(b, off, len) is that
* some of the bytes in the array b are written to the
* output stream in order; element b[off] is the first
* byte written and b[off+len-1] is the last byte written
* by this operation.
*
* The write method of OutputStream calls
* the write method of one argument on each of the bytes to be
* written out. Subclasses are encouraged to override this method and
* provide a more efficient implementation.
*
* If b is null, a
* NullPointerException is thrown.
*
* If off is negative, or len is negative, or
* off+len is greater than the length of the array
* {@code b}, then an {@code IndexOutOfBoundsException} is thrown.
*
* @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. In particular,
* an IOException is thrown if the output
* stream is closed.
*/
public void write(byte b[], int off, int len) throws IOException {
Objects.checkFromIndexSize(off, len, b.length);
// len == 0 condition implicitly handled by loop bounds
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. The general contract of flush 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.
*
* 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. *
* The flush method of OutputStream does nothing.
*
* @exception IOException if an I/O error occurs.
*/
public void flush() throws IOException {
}
/**
* Closes this output stream and releases any system resources
* associated with this stream. The general contract of close
* is that it closes the output stream. A closed stream cannot perform
* output operations and cannot be reopened.
*
* The close method of OutputStream does nothing.
*
* @exception IOException if an I/O error occurs.
*/
public void close() throws IOException {
}
}