Overview | Package | Class | Use | Tree | Deprecated | Index | Help
| JavaTM 2 Platform Std. Ed. v1.4.2
PREV CLASS NEXT CLASS | FRAMES NO FRAMES
SUMMARY: NESTED | FIELD | CONSTR | METHOD | DETAIL: FIELD | CONSTR | METHOD

## java.util.zip
Class Deflater

    java.lang.Object
      java.util.zip.Deflater

public class Deflater
extends Object

This class provides support for general purpose compression using the popular ZLIB compression library. The ZLIB compression library was initially developed as part of the PNG graphics standard and is not protected by patents. It is fully described in the specifications at the java.util.zip package description.

The following code fragment demonstrates a trivial compression and decompression of a string using `Deflater` and `Inflater`.

>      // Encode a String into bytes
>      String inputString = "blahblahblah??";
>      byte[] input = inputString.getBytes("UTF-8");

>      // Compress the bytes
>      byte[] output = new byte[100];
>      Deflater compresser = new Deflater();
>      compresser.setInput(input);
>      compresser.finish();
>      int compressedDataLength = compresser.deflate(output);

>      // Decompress the bytes
>      Inflater decompresser = new Inflater();
>      decompresser.setInput(output, 0, compressedDataLength);
>      byte[] result = new byte[100];
>      int resultLength = decompresser.inflate(result);
>      decompresser.end();

>      // Decode the bytes into a String
>      String outputString = new String(result, 0, resultLength, "UTF-8");

See Also:
  `Inflater`

Field Summary
`static int` | `BEST_COMPRESSION` Compression level for best compression.
`static int` | `BEST_SPEED` Compression level for fastest compression.
`static int` | `DEFAULT_COMPRESSION` Default compression level.
`static int` | `DEFAULT_STRATEGY` Default compression strategy.
`static int` | `DEFLATED` Compression method for the deflate algorithm (the only one currently supported).
`static int` | `FILTERED` Compression strategy best used for data consisting mostly of small values with a somewhat random distribution.
`static int` | `HUFFMAN_ONLY` Compression strategy for Huffman coding only.
`static int` | `NO_COMPRESSION` Compression level for no compression.

Constructor Summary
`Deflater()` Creates a new compressor with the default compression level.
`Deflater(int level)` Creates a new compressor using the specified compression level.
`Deflater(int level, boolean nowrap)` Creates a new compressor using the specified compression level.

Method Summary
`int` | `deflate(byte[] b)` Fills specified buffer with compressed data.
`int` | `deflate(byte[] b, int off, int len)` Fills specified buffer with compressed data.
`void` | `end()` Closes the compressor and discards any unprocessed input.
`protected void` | `finalize()` Closes the compressor when garbage is collected.
`void` | `finish()` When called, indicates that compression should end with the current contents of the input buffer.
`boolean` | `finished()` Returns true if the end of the compressed data output stream has been reached.
`int` | `getAdler()` Returns the ADLER-32 value of the uncompressed data.
`int` | `getTotalIn()` Returns the total number of bytes input so far.
`int` | `getTotalOut()` Returns the total number of bytes output so far.
`boolean` | `needsInput()` Returns true if the input data buffer is empty and setInput() should be called in order to provide more input.
`void` | `reset()` Resets deflater so that a new set of input data can be processed.
`void` | `setDictionary(byte[] b)` Sets preset dictionary for compression.
`void` | `setDictionary(byte[] b, int off, int len)` Sets preset dictionary for compression.
`void` | `setInput(byte[] b)` Sets input data for compression.
`void` | `setInput(byte[] b, int off, int len)` Sets input data for compression.
`void` | `setLevel(int level)` Sets the current compression level to the specified value.
`void` | `setStrategy(int strategy)` Sets the compression strategy to the specified value.

Methods inherited from class java.lang.Object
`clone, equals, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait`

Field Detail

### DEFLATED

    public static final int DEFLATED

  Compression method for the deflate algorithm (the only one currently supported).

  See Also:
    Constant Field Values

### NO_COMPRESSION

    public static final int NO_COMPRESSION

  Compression level for no compression.

  See Also:
    Constant Field Values

### BEST_SPEED

    public static final int BEST_SPEED

  Compression level for fastest compression.

  See Also:
    Constant Field Values

### BEST_COMPRESSION

    public static final int BEST_COMPRESSION

  Compression level for best compression.

  See Also:
    Constant Field Values

### DEFAULT_COMPRESSION

    public static final int DEFAULT_COMPRESSION

  Default compression level.

  See Also:
    Constant Field Values

### FILTERED

    public static final int FILTERED

  Compression strategy best used for data consisting mostly of small values with a somewhat random distribution. Forces more Huffman coding and less string matching.

  See Also:
    Constant Field Values

### HUFFMAN_ONLY

    public static final int HUFFMAN_ONLY

  Compression strategy for Huffman coding only.

  See Also:
    Constant Field Values

### DEFAULT_STRATEGY

    public static final int DEFAULT_STRATEGY

  Default compression strategy.

  See Also:
    Constant Field Values

Constructor Detail

### Deflater

    public Deflater(int level,
                    boolean nowrap)

  Creates a new compressor using the specified compression level. If 'nowrap' is true then the ZLIB header and checksum fields will not be used in order to support the compression format used in both GZIP and PKZIP.

Parameters:
  `level` - the compression level (0-9)
  `nowrap` - if true then use GZIP compatible compression

### Deflater

    public Deflater(int level)

  Creates a new compressor using the specified compression level. Compressed data will be generated in ZLIB format.

Parameters:
  `level` - the compression level (0-9)

### Deflater

    public Deflater()

  Creates a new compressor with the default compression level. Compressed data will be generated in ZLIB format.

Method Detail

### setInput

    public void setInput(byte[] b,
                         int off,
                         int len)

  Sets input data for compression. This should be called whenever needsInput() returns true indicating that more input data is required.

  Parameters:
    `b` - the input data bytes
    `off` - the start offset of the data
    `len` - the length of the data
  See Also:
    `needsInput()`

### setInput

    public void setInput(byte[] b)

  Sets input data for compression. This should be called whenever needsInput() returns true indicating that more input data is required.

  Parameters:
    `b` - the input data bytes
  See Also:
    `needsInput()`

### setDictionary

    public void setDictionary(byte[] b,
                              int off,
                              int len)

  Sets preset dictionary for compression. A preset dictionary is used when the history buffer can be predetermined. When the data is later uncompressed with Inflater.inflate(), Inflater.getAdler() can be called in order to get the Adler-32 value of the dictionary required for decompression.

  Parameters:
    `b` - the dictionary data bytes
    `off` - the start offset of the data
    `len` - the length of the data
  See Also:
    `Inflater.inflate(byte[], int, int)`, `Inflater.getAdler()`

### setDictionary

    public void setDictionary(byte[] b)

  Sets preset dictionary for compression. A preset dictionary is used when the history buffer can be predetermined. When the data is later uncompressed with Inflater.inflate(), Inflater.getAdler() can be called in order to get the Adler-32 value of the dictionary required for decompression.

  Parameters:
    `b` - the dictionary data bytes
  See Also:
    `Inflater.inflate(byte[], int, int)`, `Inflater.getAdler()`

### setStrategy

    public void setStrategy(int strategy)

  Sets the compression strategy to the specified value.

  Parameters:
    `strategy` - the new compression strategy
  Throws:
    `IllegalArgumentException` - if the compression strategy is invalid

### setLevel

    public void setLevel(int level)

  Sets the current compression level to the specified value.

  Parameters:
    `level` - the new compression level (0-9)
  Throws:
    `IllegalArgumentException` - if the compression level is invalid

### needsInput

    public boolean needsInput()

  Returns true if the input data buffer is empty and setInput() should be called in order to provide more input.

  Returns:
    true if the input data buffer is empty and setInput() should be called in order to provide more input

### finish

    public void finish()

  When called, indicates that compression should end with the current contents of the input buffer.

### finished

    public boolean finished()

  Returns true if the end of the compressed data output stream has been reached.

  Returns:
    true if the end of the compressed data output stream has been reached

### deflate

    public int deflate(byte[] b,
                       int off,
                       int len)

  Fills specified buffer with compressed data. Returns actual number of bytes of compressed data. A return value of 0 indicates that needsInput() should be called in order to determine if more input data is required.

  Parameters:
    `b` - the buffer for the compressed data
    `off` - the start offset of the data
    `len` - the maximum number of bytes of compressed data
  Returns:
    the actual number of bytes of compressed data

### deflate

    public int deflate(byte[] b)

  Fills specified buffer with compressed data. Returns actual number of bytes of compressed data. A return value of 0 indicates that needsInput() should be called in order to determine if more input data is required.

  Parameters:
    `b` - the buffer for the compressed data
  Returns:
    the actual number of bytes of compressed data

### getAdler

    public int getAdler()

  Returns the ADLER-32 value of the uncompressed data.

  Returns:
    the ADLER-32 value of the uncompressed data

### getTotalIn

    public int getTotalIn()

  Returns the total number of bytes input so far.

  Returns:
    the total number of bytes input so far

### getTotalOut

    public int getTotalOut()

  Returns the total number of bytes output so far.

  Returns:
    the total number of bytes output so far

### reset

    public void reset()

  Resets deflater so that a new set of input data can be processed. Keeps current compression level and strategy settings.

### end

    public void end()

  Closes the compressor and discards any unprocessed input. This method should be called when the compressor is no longer being used, but will also be called automatically by the finalize() method. Once this method is called, the behavior of the Deflater object is undefined.

### finalize

    protected void finalize()

  Closes the compressor when garbage is collected.

  Overrides:
    `finalize` in class `Object`

Overview | Package | Class | Use | Tree | Deprecated | Index | Help
| JavaTM 2 Platform Std. Ed. v1.4.2
PREV CLASS NEXT CLASS | FRAMES NO FRAMES
SUMMARY: NESTED | FIELD | CONSTR | METHOD | DETAIL: FIELD | CONSTR | METHOD

Submit a bug or feature
For further API reference and developer documentation, see Java 2 SDK SE Developer Documentation. That documentation contains more detailed, developer-targeted descriptions, with conceptual overviews, definitions of terms, workarounds, and working code examples.

Copyright 2003 Sun Microsystems, Inc. All rights reserved. Use is subject to license terms. Also see the documentation redistribution policy.