Chapter 18
The java.util.zip Package

GZIPOutputStream

Name

GZIPOutputStream

Synopsis

Class Name:

java.util.zip.GZIPOutputStream

Superclass:

java.util.zip.DeflaterOutputStream

Immediate Subclasses:

None

Interfaces Implemented:

None

Availability:

New as of JDK 1.1

The GZIPOutputStream class compresses data using the GZIP format. To use it, simply construct a GZIPOutputStream that wraps a regular output stream and use the write() methods to write compressed data.

Class Summary

public class java.util.zip.GZIPOutputStream
             extends java.util.zip.DeflaterOutputStream {
  // Variables
  protected CRC32 crc;
  // Constructors
  public GZIPOutputStream(OutputStream out);
  public GZIPOutputStream(OutputStream out, int size);
  // Instance Methods
  public void close();
  public void finish();
  public synchronized void write(byte[] buf, int off, int len);
}

Variables

crc

protected CRC32 crc

Description: A checksum that is updated with the uncompressed stream data. The checksum value is written into the GZIP trailer.

Constructors

GZIPOutputStream

public GZIPOutputStream(OutputStream out) throws IOException

Parameters

out: The underlying output stream.

Throws

IOException: If an error occurs while writing the GZIP header.

Description

This constructor creates a GZIPOutputStream that writes compressed data to the given OutputStream. The GZIPOutputStream uses a compression buffer with the default size of 512 bytes.

 public GZIPOutputStream(OutputStream out, int size) throws IOException

Parameters

out

The underlying output stream.

size

The size of the output buffer.

Throws

IOException: If an error occurs while writing the GZIP header.

Description

This constructor creates a GZIPOutputStream that writes compressed data to the given OutputStream. The GZIPOutputStream uses a compression buffer of the given size.

Instance Methods

close

public void close() throws IOException

Throws

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

Overrides

DeflaterOutputStream.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.

Overrides

DeflaterOutputStream.finish()

Description

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

write

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

Parameters

buf

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

DeflaterOutputStream.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.

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(int)`	`DeflaterOutputStream`	`write(byte[])`	`FilterOutputStream`