edu.msoe.jones.huffmantree

Class HuffmanTreeUtilities

java.lang.Object

edu.msoe.jones.huffmantree.HuffmanTreeUtilities

public class HuffmanTreeUtilities
extends java.lang.Object

A Class that contains various methods and a few classes that use the HuffmanTree abstract class to build Huffman Trees and encode and decode .txt files using Huffman encoding.

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
(package private) static class	HuffmanTreeUtilities.HuffmanLeaf A class that defines a leaf node of a HuffmanTree.
private static class	HuffmanTreeUtilities.HuffmanNode A class that defines an inner node of a HuffmanTree.

Field Summary

Fields

Modifier and Type	Field and Description
private static int	ASCII_VALUES Default number of characters in extended ASCII
private static java.util.HashMap<java.lang.Character,java.lang.String>	CODE_TABLE HashMap that who's entries contain an ASCII character and a String containing it's Huffman binary code.

Constructor Summary

Constructors

Constructor and Description
HuffmanTreeUtilities()

Method Summary

Modifier and Type	Method and Description
private static void	buildTable(HuffmanTree tree, java.lang.StringBuffer prefix) A helper method that builds a table of mappings for ASCII characters and their Huffman encodings from a complete Huffman Tree
static HuffmanTree	buildTree(int[] characterFrequencies) A method that builds a Huffman Tree, based on an array of character frequencies.
static int[]	calculateFrequencies(java.lang.String input) A method that calculates the frequencies of all of the characters in a given String and stores those characters in an array, using the character's ASCII numbers as their index.
static void	compress(HuffmanTree tree, java.lang.String filename, java.lang.String input) A method that saves text stored in a String to a compressed binary file using Huffman encoding
static java.lang.String	decompress(HuffmanTree tree, java.io.File file) A method that decompresses a binary file created using Huffman encoding.
private static void	inorderTraversal(HuffmanTree tree, java.lang.StringBuffer prefix, Traverse traverse) A helper method that does an in-order traversal of a Huffman tree.
static void	printCodes(HuffmanTree tree, java.lang.StringBuffer prefix) A helper method that prints a table of the ASCII character and Huffman Code mapping from a given Huffman Tree

Methods inherited from class java.lang.Object

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

Field Detail

ASCII_VALUES

private static final int ASCII_VALUES

Default number of characters in extended ASCII

See Also:

Constant Field Values

CODE_TABLE

private static final java.util.HashMap<java.lang.Character,java.lang.String> CODE_TABLE

HashMap that who's entries contain an ASCII character and a String containing it's Huffman binary code.

Constructor Detail

HuffmanTreeUtilities

public HuffmanTreeUtilities()

Method Detail

calculateFrequencies

public static int[] calculateFrequencies(java.lang.String input)

A method that calculates the frequencies of all of the characters in a given String and stores those characters in an array, using the character's ASCII numbers as their index.

Parameters:

input - The String to calculate frequencies from

Returns:

The array of frequencies for each character in the ASCII table

buildTree

public static HuffmanTree buildTree(int[] characterFrequencies)

A method that builds a Huffman Tree, based on an array of character frequencies.

Parameters:

characterFrequencies - The frequencies used to build the Huffman Tree

Returns:

A complete Huffman Tree

printCodes

public static void printCodes(HuffmanTree tree,
                              java.lang.StringBuffer prefix)

A helper method that prints a table of the ASCII character and Huffman Code mapping from a given Huffman Tree

Parameters:

tree - A complete Huffman Tree

prefix - A StringBuffer used to build the binary mapping

buildTable

private static void buildTable(HuffmanTree tree,
                               java.lang.StringBuffer prefix)

A helper method that builds a table of mappings for ASCII characters and their Huffman encodings from a complete Huffman Tree

Parameters:

tree - The complete Huffman Tree containing the encoding

prefix - A StringBuffer used to build the table

compress

public static void compress(HuffmanTree tree,
                            java.lang.String filename,
                            java.lang.String input)

A method that saves text stored in a String to a compressed binary file using Huffman encoding

Parameters:

tree - The Huffman Tree that contains the encoding

filename - The name of the file to save the compressed data to

input - A String containing text to save to the binary file

decompress

public static java.lang.String decompress(HuffmanTree tree,
                                          java.io.File file)

A method that decompresses a binary file created using Huffman encoding. The resulting text will be stored in a String. This method uses a BitInputStream to read the binary data bit by bit.

Parameters:

tree - The Huffman Tree containing the encoding

file - The binary file containing the encoded text

Returns:

A String containing the decoded text

inorderTraversal

private static void inorderTraversal(HuffmanTree tree,
                                     java.lang.StringBuffer prefix,
                                     Traverse traverse)

A helper method that does an in-order traversal of a Huffman tree. When a leaf node is encountered, that node will be processed by the process method defined in a given Traverse interface

Parameters:

tree - The Huffman Tree to be traversed

prefix - A StringBuffer used to keep track of the current path

traverse - A functional interface that defines what occurs when visiting a leaf node