Chapter 11
The java.io Package

OutputStream

Name

OutputStream

Synopsis

Class Name:

java.io.OutputStream

Superclass:

java.lang.Object

Immediate Subclasses:

java.io.ByteArrayOutputStream,

java.io.FileOutputStream,

java.io.FilterOutputStream,

java.io.ObjectOutputStream,

java.io.PipedOutputStream

Interfaces Implemented:

None

Availability:

JDK 1.0 or later

The OutputStream class is an abstract class that is the superclass of all classes that represent output byte streams. OutputStream defines the basic output methods that all output streams provide. A similar hierarchy of classes, based around Writer, deals with character streams instead of byte streams.

OutputStream is designed so that write(byte[]) and write(byte[], int, int) call write(int b). Thus, a subclass can simply override write(), and all the write methods will work. However, for efficiency's sake, write(byte[], int, int) should also be overridden with a method that can write a block of data more efficiently than writing each byte separately.

Some OutputStream subclasses may implement buffering to increase efficiency. OutputStream provides a method, flush(), that tells the OutputStream to write any buffered output to the underlying device, which may be a disk drive or a network.

Class Summary

public abstract class java.io.OutputStream extends java.lang.Object {
  // Instance Methods
  public void close();
  public void flush();
  public abstract void write(int b);
  public void write(byte[] b);
  public void write(byte[] b, int off, int len);
}

Instance Methods

close

public void close() throws IOException

Throws

IOException: If any kind of I/O error occurs.

Description

This method closes the output stream and releases any resources associated with it.

The implementation of the close() method in OutputStream does nothing; a subclass should override this method to handle cleanup for the stream.

flush

public void flush() throws IOException

Throws

IOException: If any kind of I/O error occurs.

Description

This method forces any bytes that may be buffered by the output stream to be written.

The implementation of flush() in OutputStream does nothing; a subclass should override this method as needed.

write

public abstract void write(int b) throws IOException

Parameters

b: The value to write to the stream.

Throws

IOException: If any kind of I/O error occurs.

Description

This method writes a byte of output. The method blocks until the byte is actually written.

A subclass of OutputStream must implement this method.

public void write(byte[] b) throws IOException

Parameters

b: An array of bytes to write to the stream.

Throws

IOException: If any kind of I/O error occurs.

Description

This method writes the bytes from the given array by calling write(b, 0, b.length). The method blocks until the bytes are actually written.

A subclass does not usually need to override this method, as it can override write(byte[], int, int) and have write(byte[]) work automatically.

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

Parameters

b

An array of bytes to write to the stream.

off

An offset into the byte array.

len

The number of bytes to write.

Throws

IOException: If any kind of I/O error occurs.

Description

This method writes len bytes of output from the given array, starting at offset off. The method blocks until the bytes are actually written.

The implementation of this method in OutputStream uses write(int) repeatedly to write the bytes. Although it is not strictly necessary, a subclass should override this method to write a block of data more efficiently.

Inherited Methods

Method	Inherited From	Method	Inherited From
`clone()`	`Object`	`equals(Object)`	`Object`
`finalize()`	`Object`	`getClass()`	`Object`
`hashCode()`	`Object`	`notify()`	`Object`
`notifyAll()`	`Object`	`toString()`	`Object`
`wait()`	`Object`	`wait(long)`	`Object`
`wait(long, int)`	`Object`