com.coyotegulch.jisp

Class Huffman

java.lang.Object

com.coyotegulch.jisp.Huffman

public class Huffman
extends java.lang.Object

Compresses and decompresses objects using the Huffman algorithm. Huffman encoding creates a set of codes for which the shortest code represents the most common piece of data. Codes created by the Huffman algorithm require a file to be analyzed, counting bytes to determine their frequency. From the frequencies, the Huffman algorithm builds a table of codes used to compress the information. Including the table of codes with the compressed data allows the original file to be reconstructed.

To be most effective, Huffman encoding uses a variable length code, where no code is a prefix of another, which makes decompression easier by allowing the extraction of the file bit-by-bit. The shortest codes are assigned to the most common characters, with infrequent characters receiving longer codes.

Objects to be compressed must be Serializable.

See Also:

HuffmanEncoded

Constructor Summary

Constructors

Constructor and Description
Huffman()

Method Summary

Modifier and Type	Method and Description
static java.lang.Object	decode(HuffmanEncoded enc) Decodes a compressed object using the Huffman algorithm.
static HuffmanEncoded	encode(java.lang.Object obj) Encodes an object using Huffman compression.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

Huffman

public Huffman()

Method Detail

encode

public static HuffmanEncoded encode(java.lang.Object obj)
                             throws java.io.IOException

Encodes an object using Huffman compression.

Parameters:

obj - serializable object to be compressed

Returns:

a new HuffmanEncoded object containing the compressed object and its encoding table

Throws:

java.io.IOException - when an I/O exception is thrown by an underlying java.io.* class

See Also:

HuffmanEncoded

decode

public static java.lang.Object decode(HuffmanEncoded enc)
                               throws java.io.IOException,
                                      java.lang.ClassNotFoundException

Decodes a compressed object using the Huffman algorithm.

Parameters:

enc - object to be decompressed

Returns:

the decompressed Object

Throws:

java.io.IOException - when an I/O exception is thrown by an underlying java.io.* class

java.lang.ClassNotFoundException - when an explicit cast fails

See Also:

HuffmanEncoded