Chapter 18
The java.util.zip Package

DeflaterOutputStream

Name

Synopsis

Class Name:

java.util.zip.DeflaterOutputStream

Superclass:

java.io.FilterOutputStream

Immediate Subclasses:

java.util.zip.GZIPOutputStream, java.util.zip.ZipOutputStream

Interfaces Implemented:

None

Availability:

New as of JDK 1.1

The DeflaterOutputStream class represents an OutputStream with an associated Deflater. In other words, a DeflaterOutputStream wraps a regular output stream, so that data written to the stream is compressed and written to the underlying stream. Two subclasses, GZIPOutputStream and ZipOutputStream, write compressed data in widely-recognized formats.

Class Summary

public class java.util.zip.DeflaterOutputStream 
             extends java.io.FilterOutputStream {
  // Variables
  protected byte[] buf;
  protected Deflater def;
  // Constructors
  public DeflaterOutputStream(OutputStream out);
  public DeflaterOutputStream(OutputStream out, Deflater def);
  public DeflaterOutputStream(OutputStream out, Deflater def, int size);
  // Public Instance Methods
  public void close();
  public void finish();
  public void write(int b);
  public void write(byte[] b, int off, int len);
  // Protected Instance Methods
  protected void deflate();
}

Variables

buf

protected byte[] buf

Description: A buffer that holds the compressed data that is written to the underlying stream.

def

protected Deflater def

Description: The Deflater object that is used internally.

Constructors

DeflaterOutputStream

public DeflaterOutputStream(OutputStream out)

Parameters

out: The underlying output stream.

Description

This constructor creates a DeflaterOutputStream that writes data to the given OutputStream. Before being written, the data is compressed by a default Deflater. The DeflaterOutputStream uses a compression buffer with the default size of 512 bytes.

public DeflaterOutputStream(OutputStream out, Deflater def)

Parameters

out

The underlying output stream.

def

The Deflater object.

Description

This constructor creates a DeflaterOutputStream that writes data to the given OutputStream. Before being written, the data is compressed by the given Deflater. The DeflaterOutputStream uses a compression buffer with the default size of 512 bytes.

 public DeflaterOutputStream(OutputStream out, Deflater def, int size)

Parameters

out

The underlying output stream.

def

The Deflater object.

size

The size of the output buffer.

Description

Public Instance Methods

close

public void close() throws IOException

Throws

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

Overrides

FilterOutputStream.close()

Description

This method closes the stream and releases any system resources that are associated with it.

finish

public void finish() throws IOException

Throws

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

Description

This method finishes writing compressed data to the underlying stream without closing it.

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

FilterOutputStream.write(int)

Description

This method compresses a byte that contains the lowest eight bits of the given integer value and writes it to the underlying OutputStream. The method blocks until the byte is written.

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

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

Description

This method takes len bytes from the given buffer, starting at off, and compresses them. The method then writes the compressed data to the underlying OutputStream. The method blocks until all of the bytes have been written.

Protected Instance Methods

deflate

protected void deflate() throws IOException

Throws

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

Description

This method asks the internal Deflater to compress the data in the buffer for this DeflaterOutputStream. The method then writes the compressed contents of the buffer to the underlying stream. The method is called by both write() methods.

Inherited Methods

Method	Inherited From	Method	Inherited From
`clone()`	`Object`	`equals(Object)`	`Object`
`finalize()`	`Object`	`flush()`	`FilterOutputStream`
`getClass()`	`Object`	`hashCode()`	`Object`
`notify()`	`Object`	`notifyAll()`	`Object`
`toString()`	`Object`	`wait()`	`Object`
`wait(long)`	`Object`	`wait(long, int)`	`Object`
`write(byte[])`	`FilterOutputStream`