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/*
* Copyright (c) 1994, 2019, Oracle and/or its affiliates. All rights reserved.
* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
*
* This code is free software; you can redistribute it and/or modify it
* under the terms of the GNU General Public License version 2 only, as
* published by the Free Software Foundation. Oracle designates this
* particular file as subject to the "Classpath" exception as provided
* by Oracle in the LICENSE file that accompanied this code.
*
* This code is distributed in the hope that it will be useful, but WITHOUT
* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
* version 2 for more details (a copy is included in the LICENSE file that
* accompanied this code).
*
* You should have received a copy of the GNU General Public License version
* 2 along with this work; if not, write to the Free Software Foundation,
* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
*
* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
* or visit www.oracle.com if you need additional information or have any
* questions.
*/
package java.io;
import java.util.Objects;
/**
* This abstract class is the superclass of all classes representing
* an output stream of bytes. An output stream accepts output bytes
* and sends them to some sink.
*
* Applications that need to define a subclass of
* {@code 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 {
/**
* Constructor for subclasses to call.
*/
public OutputStream() {}
/**
* 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 {@code 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 {@code b}. The 24
* high-order bits of {@code b} are ignored.
*
* Subclasses of {@code OutputStream} must provide an
* implementation for this method.
*
* @param b the {@code byte}.
* @throws IOException if an I/O error occurs. In particular,
* an {@code IOException} may be thrown if the
* output stream has been closed.
*/
public abstract void write(int b) throws IOException;
/**
* Writes {@code b.length} bytes from the specified byte array
* to this output stream. The general contract for {@code write(b)}
* is that it should have exactly the same effect as the call
* {@code write(b, 0, b.length)}.
*
* @param b the data.
* @throws 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 {@code len} bytes from the specified byte array
* starting at offset {@code off} to this output stream.
* The general contract for {@code write(b, off, len)} is that
* some of the bytes in the array {@code b} are written to the
* output stream in order; element {@code b[off]} is the first
* byte written and {@code b[off+len-1]} is the last byte written
* by this operation.
*
* The {@code write} method of {@code 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 {@code b} is {@code null}, a
* {@code NullPointerException} is thrown.
*
* If {@code off} is negative, or {@code len} is negative, or
* {@code 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.
* @throws IOException if an I/O error occurs. In particular,
* an {@code 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 {@code 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 {@code flush} method of {@code OutputStream} does nothing.
*
* @throws 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 {@code close}
* is that it closes the output stream. A closed stream cannot perform
* output operations and cannot be reopened.
*
* The {@code close} method of {@code OutputStream} does nothing.
*
* @throws IOException if an I/O error occurs.
*/
public void close() throws IOException {
}
}