Module java.base

Package java.io

Class OutputStream

java.lang.Object

java.io.OutputStream

All Implemented Interfaces:

Closeable, Flushable, AutoCloseable

Direct Known Subclasses:

ByteArrayOutputStream, FileOutputStream, FilterOutputStream, ObjectOutputStream, PipedOutputStream

public abstract class OutputStream
extends Object
implements Closeable, Flushable

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 OutputStream must always provide at least a method that writes one byte of output.

Since:

1.0

See Also:

• BufferedOutputStream
• ByteArrayOutputStream
• DataOutputStream
• FilterOutputStream
• InputStream
• write(int)

Constructor Summary

Constructors

Constructor	Description
OutputStream()	Constructor for subclasses to call.

Method Summary

Modifier and Type	Method	Description
void	close()	Closes this output stream and releases any system resources associated with this stream.
void	flush()	Flushes this output stream and forces any buffered output bytes to be written out.
static OutputStream	nullOutputStream()	Returns a new OutputStream which discards all bytes.
void	write(byte[] b)	Writes b.length bytes from the specified byte array to this output stream.
void	write(byte[] b, int off, int len)	Writes len bytes from the specified byte array starting at offset off to this output stream.
abstract void	write(int b)	Writes the specified byte to this output stream.

Methods declared in class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Details

OutputStream

public OutputStream()

Constructor for subclasses to call.

Method Details

nullOutputStream

public static OutputStream nullOutputStream()

Returns a new OutputStream which discards all bytes. The returned stream is initially open. The stream is closed by calling the close() method. Subsequent calls to close() have no effect.

While the stream is open, the write(int), write(byte[]), and write(byte[], int, int) methods do nothing. After the stream has been closed, these methods all throw IOException.

The flush() method does nothing.

Returns:

an OutputStream which discards all bytes

Since:

11

write

public abstract void write(int b)
                    throws IOException

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.

Parameters:

b - the byte.

Throws:

IOException - if an I/O error occurs. In particular, an IOException may be thrown if the output stream has been closed.

write

public void write(byte[] 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).

Parameters:

b - the data.

Throws:

IOException - if an I/O error occurs.

See Also:

• write(byte[], int, int)

write

public void write(byte[] b,
 int off,
 int len)
           throws IOException

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.

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 b, then an IndexOutOfBoundsException is thrown.

API Note:

Subclasses are encouraged to override this method and provide a more efficient implementation.

Implementation Requirements:

The write method of OutputStream calls the write method of one argument on each of the bytes to be written out.

Parameters:

b - the data.

off - the start offset in the data.

len - the number of bytes to write.

Throws:

IOException - if an I/O error occurs. In particular, an IOException is thrown if the output stream is closed.

IndexOutOfBoundsException - If off is negative, len is negative, or len is greater than b.length - off

flush

public void flush()
           throws IOException

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.

Specified by:

flush in interface Flushable

Implementation Requirements:

The flush method of OutputStream does nothing.

Throws:

IOException - if an I/O error occurs.

close

public void close()
           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.

Specified by:

close in interface AutoCloseable

Specified by:

close in interface Closeable

Implementation Requirements:

The close method of OutputStream does nothing.

Throws:

IOException - if an I/O error occurs.