LZW-compressor

This is an implementation of the LZW algorithm

LZW.java contains an encode and decode method to compress and decompress a string using the LZW compression algorithm. The LZW algorithm is an adaptive model which progessively leanrs and updates based on the incoming text. It uses a dictionary and the compressed text consists of positions of string patterns in the dictionary.

Set-up

To set up the compressor, first create an instance of the LZW class.

LZW compressor = new LZW();

You can then declare the string you wish to compress.

String stringToEncode = "aababacbaacbaadaaa";

The final set-up stage is to create the initial dictionary for compression and for decompression. This dictionary will contain only the letters that appear in the string you wish to encode.

Hashtable<String, Integer> initialDictionaryEncode = compressor.makeInitialDictionaryEncode(stringToEncode);
Hashtable<Integer, String> initialDictionaryDecode = compressor.makeInitialDictionaryDecode(stringToEncode);

Compress

To compress the string, call the encode method.

ArrayList<Integer> compressedString = compressor.encode(stringToEncode, initialDictionaryEncode);

Decompress

To decompress the list of dictionary positions, call the decode method.

String decompressedString = compressor.decode(compressedString, initialDictionaryDecode);