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public class

Deflater

extends Object
java.lang.Object
   ↳ java.util.zip.Deflater

Class Overview

The Deflater class is used to compress bytes using the DEFLATE compression algorithm. Deflation is performed by the ZLIB compression library.

See Also

Summary

Constants
int BEST_COMPRESSION
int BEST_SPEED
int DEFAULT_COMPRESSION
int DEFAULT_STRATEGY
int DEFLATED
int FILTERED
int HUFFMAN_ONLY
int NO_COMPRESSION
Public Constructors
Deflater()
Constructs a new Deflater instance with default compression level and strategy.
Deflater(int level)
Constructs a new Deflater instance with compression level level and default compression strategy.
Deflater(int level, boolean noHeader)
Constructs a new Deflater instance with compression level level and default compression strategy.
Public Methods
int deflate(byte[] buf)
Deflates data into the supplied buffer
synchronized int deflate(byte[] buf, int off, int nbytes)
Deflates data into the supplied buffer using the region from off to nbytes - 1.
synchronized void end()
Frees all resources held onto by this Deflater.
synchronized void finish()
Indicates to the Deflater that all uncompressed input has been provided to it.
synchronized boolean finished()
Returns whether or not all provided data has been successfully compressed.
synchronized int getAdler()
Returns the Adler32 checksum of uncompressed data currently read.
synchronized long getBytesRead()
Returns a long int of total number of bytes read by the Deflater.
synchronized long getBytesWritten()
Returns a long int of total number of bytes of read by the Deflater.
synchronized int getTotalIn()
Returns the total number of bytes of input consumed by the deflater.
synchronized int getTotalOut()
Returns the total number of compressed bytes output by this Deflater.
synchronized boolean needsInput()
Indicates whether or not all bytes of uncompressed input have been consumed by the Deflater.
synchronized void reset()
Resets the Deflater to accept new input without affecting any previously made settings for the compression strategy or level.
synchronized void setDictionary(byte[] buf, int off, int nbytes)
Sets the dictionary to be used for compression by this Deflater.
void setDictionary(byte[] buf)
synchronized void setInput(byte[] buf, int off, int nbytes)
Sets the input buffer the Deflater will use to extract uncompressed bytes for later compression.
void setInput(byte[] buf)
Sets the input buffer the Deflater will use to extract uncompressed bytes for later compression.
synchronized void setLevel(int level)
Sets the compression level to be used when compressing data.
synchronized void setStrategy(int strategy)
Sets the compression strategy to be used.
Protected Methods
void finalize()
Called by the virtual machine when there are no longer any (non-weak) references to the receiver.
[Expand]
Inherited Methods
From class java.lang.Object

Constants

public static final int BEST_COMPRESSION

Constant Value: 9 (0x00000009)

public static final int BEST_SPEED

Constant Value: 1 (0x00000001)

public static final int DEFAULT_COMPRESSION

Constant Value: -1 (0xffffffff)

public static final int DEFAULT_STRATEGY

Constant Value: 0 (0x00000000)

public static final int DEFLATED

Constant Value: 8 (0x00000008)

public static final int FILTERED

Constant Value: 1 (0x00000001)

public static final int HUFFMAN_ONLY

Constant Value: 2 (0x00000002)

public static final int NO_COMPRESSION

Constant Value: 0 (0x00000000)

Public Constructors

public Deflater ()

Constructs a new Deflater instance with default compression level and strategy.

public Deflater (int level)

Constructs a new Deflater instance with compression level level and default compression strategy. THe compression level provided must be between 0 and 9.

Parameters
level the compression level to use

public Deflater (int level, boolean noHeader)

Constructs a new Deflater instance with compression level level and default compression strategy. If the noHeader parameter is specified then no ZLIB header will be written as part of the compressed output. The compression level specified must be between 0 and 9.

Parameters
level the compression level to use
noHeader if true do not write the ZLIB header

Public Methods

public int deflate (byte[] buf)

Deflates data into the supplied buffer

Parameters
buf buffer to store compressed data
Returns
  • number of bytes of compressed data stored

public synchronized int deflate (byte[] buf, int off, int nbytes)

Deflates data into the supplied buffer using the region from off to nbytes - 1.

Parameters
buf buffer to store compressed data
off offset inf buf to start storing data
nbytes number of bytes of compressed data to store in buf
Returns
  • number of bytes of compressed data stored

public synchronized void end ()

Frees all resources held onto by this Deflater. Any unused input or output is discarded. This is also called from the finalize method.

See Also

public synchronized void finish ()

Indicates to the Deflater that all uncompressed input has been provided to it.

See Also

public synchronized boolean finished ()

Returns whether or not all provided data has been successfully compressed.

Returns
  • true if all data has been compressed, false otherwise

public synchronized int getAdler ()

Returns the Adler32 checksum of uncompressed data currently read. If a preset dictionary is used getAdler() will return the Adler32 checksum of the dictionary used.

Returns
  • The Adler32 checksum of uncompressed data or preset dictionary if used
See Also

public synchronized long getBytesRead ()

Returns a long int of total number of bytes read by the Deflater. This method performs the same as getTotalIn except it returns a long value instead of an integer

Returns
  • bytes exactly read by deflater

public synchronized long getBytesWritten ()

Returns a long int of total number of bytes of read by the Deflater. This method performs the same as getTotalOut except it returns a long value instead of an integer

Returns
  • bytes exactly write by deflater

public synchronized int getTotalIn ()

Returns the total number of bytes of input consumed by the deflater.

Returns
  • number of bytes of input read.

public synchronized int getTotalOut ()

Returns the total number of compressed bytes output by this Deflater.

Returns
  • number of compressed bytes output.

public synchronized boolean needsInput ()

Indicates whether or not all bytes of uncompressed input have been consumed by the Deflater. If needsInput() returns true setInput() must be called before deflation can continue. If all bytes of uncompressed data have been provided to the Deflater finish() must be called to ensure the compressed data is output.

Returns
  • True if input is required for deflation to continue, false otherwise
See Also

public synchronized void reset ()

Resets the Deflater to accept new input without affecting any previously made settings for the compression strategy or level. This operation must be called after finished() returns true if the Deflater is to be reused.

See Also

public synchronized void setDictionary (byte[] buf, int off, int nbytes)

Sets the dictionary to be used for compression by this Deflater. setDictionary() can only be called if this Deflater supports the writing of ZLIB headers. This is the default behaviour but can be overridden using Deflater(int, boolean).

See Also

public void setDictionary (byte[] buf)

public synchronized void setInput (byte[] buf, int off, int nbytes)

Sets the input buffer the Deflater will use to extract uncompressed bytes for later compression. Input will be taken from the buffer region starting at off and ending at nbytes - 1.

public void setInput (byte[] buf)

Sets the input buffer the Deflater will use to extract uncompressed bytes for later compression.

public synchronized void setLevel (int level)

Sets the compression level to be used when compressing data. The compression level must be a value between 0 and 9. This value must be set prior to calling setInput().

Parameters
level compression level to use
Throws
IllegalArgumentException If the compression level is invalid.

public synchronized void setStrategy (int strategy)

Sets the compression strategy to be used. The strategy must be one of FILTERED, HUFFMAN_ONLY or DEFAULT_STRATEGY.This value must be set prior to calling setInput().

Parameters
strategy compression strategy to use
Throws
IllegalArgumentException If the strategy specified is not one of FILTERED, HUFFMAN_ONLY or DEFAULT_STRATEGY.

Protected Methods

protected void finalize ()

Called by the virtual machine when there are no longer any (non-weak) references to the receiver. Subclasses can use this facility to guarantee that any associated resources are cleaned up before the receiver is garbage collected. Uncaught exceptions which are thrown during the running of the method cause it to terminate immediately, but are otherwise ignored.

Note: The virtual machine assumes that the implementation in class Object is empty.