Chapter 11
The java.io Package

FilterOutputStream

Name

FilterOutputStream

Synopsis

Class Name:

java.io.FilterOutputStream

Superclass:

java.io.ObjectStream

Immediate Subclasses:

java.io.BufferedOutputStream,

java.io.DataOutputStream,

java.io.PrintStream,

java.util.zip.CheckedOutputStream,

java.util.zip.DeflaterOutputStream

Interfaces Implemented:

None

Availability:

JDK 1.0 or later

The FilterOutputStream class is the superclass of all of the output stream classes that filter output. Each of the subclasses of FilterOutputStream works by wrapping an existing output stream, called the underlying output stream, and providing additional functionality. The methods of FilterOutputStream simply override the methods of OutputStream with versions that call the corresponding methods of the underlying stream.

FilterOutputStream cannot be instantiated directly; it must be subclassed. An instance of one of the subclasses of FilterOutputStream is constructed with another OutputStream object. The methods of a subclass of FilterOutputStream should override some methods in order to extend their behavior or provide some sort of filtering.

Class Summary

public class java.io.FilterOutputStream extends java.io.OutputStream {
  // Variables
  protected OutputStream out;
  // Constructors
  public FilterOutputStream(OutputStream out);
  // Instance Methods
  public void close();
  public void flush();
  public void write(int b);
  public void write(byte[] b); 
  public void write(byte[] b, int off, int len); 
}

Variables

out

protected OutputStream out

Description: The underlying stream that this FilterOutputStream wraps or filters.

Constructors

FilterOutputStream

public FilterOutputStream(OutputStream out)

Parameters

out: The output stream to filter.

Description

This constructor creates a FilterOutputStream that sends its data to out.

Instance Methods

close

public void close() throws IOException

Throws

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

Overrides

OutputStream.close()

Description

This method calls the close() method of the underlying stream, which releases any system resources associated with this object.

flush

public void flush() throws IOException

Throws

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

Overrides

OutputStream.flush()

Description

This method calls the flush() method of the underlying stream, which forces any bytes that may be buffered by this FilterOutputStream to be written to the underlying device.

write

public void write(int b) throws IOException

Parameters

b: The value to write.

Throws

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

Overrides

OutputStream.write(int)

Description

This method writes a byte containing the low-order eight bits of the given integer value. The method calls the write(int) method of the underlying stream.

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.

Overrides

OutputStream.write(byte[])

Description

This method writes the bytes contained in the given array. To accomplish this, it calls write(b, 0, b.length). Subclasses need override only write(byte[], int, int) for this method to 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.

Overrides

OutputStream.write(byte[], int, int)

Description

This method writes len bytes contained in the given array, starting at offset off. It does this by calling write(int) for each element to be written in the array. This is inefficient, so subclasses should override write(byte[], int, int) with a method that efficiently writes a block of data.

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`