Lab 11: Morse Code Encoder

Learning Outcomes

• Have a thorough understanding of commonly used library data structures
• Use data structures in software design and implementation
• Describe how elements are added to a hash table
• Describe the chaining method for dealing with collisions within a hash table
• Write a hash table implementation (using chaining) that includes the following methods: put(K key, V value), containsKey(Object key), and get(Object key).
• Use a hash table to implement a Map
• Apply the Map<K, V> interface defined in the Java Collections Framework

Overview

Video overview

In this lab, you are going to implement a program that encodes messages written in morse code. You will use a map (that you will implement) to look up the morse code associated with each English character.

Your program's GUI will appear similar to the one from lab 9, however we will be implementing menus in place of buttons to select actions.

Sample Results

Running your program on this file:

A space should be placed between each encoded character.

A **'' ''** should be placed between each word.

Line breaks in the input file should be replicated in the encoded file.

should display the following in an Alert after encoding:

Warning: skipping: *
Warning: skipping: *
Warning: skipping: '
Warning: skipping: '
Warning: skipping: '
Warning: skipping: '
Warning: skipping: *
Warning: skipping: *

and produce the following output:

.- .-... ... .--. .- -.-. . .-... ... .... --- ..- .-.. -.. .-... -... . .-... .--. .-.. .- -.-. . -.. .-... -... . - .-- . . -. .-... . .- -.-. .... .-... . -. -.-. --- -.. . -.. .-... -.-. .... .- .-. .- -.-. - . .-. .-.-.- .-.-
.-.-
.- .-... .-... .-... ... .... --- ..- .-.. -.. .-... -... . .-... .--. .-.. .- -.-. . -.. .-... -... . - .-- . . -. .-... . .- -.-. .... .-... .-- --- .-. -.. .-.-.- .-.-
.-.-
.-.. .. -. . .-... -... .-. . .- -.- ... .-... .. -. .-... - .... . .-... .. -. .--. ..- - .-... ..-. .. .-.. . .-... ... .... --- ..- .-.. -.. .-... -... . .-... .-. . .--. .-.. .. -.-. .- - . -.. .-... .. -. .-... - .... . .-... . -. -.-. --- -.. . -.. .-... ..-. .. .-.. . .-.-.- .-.-

Implementation

In this lab, in addition to your MorseDriver class that will launch your GUI, you write and test three classes: MorseEncoder, HashMap, and your Controller class.

MorseEncoder

Your MorseEncoder class must contain the following three methods:

• static void loadTable(Path path) — Accepts a Path object containing the morsecode.txt file as and argument and populates a Map object with the codes and their corresponding symbols. The method calls the put() method from the HashMap class multiple times in order to populate the hash table.
• static String encodeMessage(String message) — Accepts a message and returns the encoded message. Note that this method must handle lowercase characters even if not in the table.
• playTone(boolean dot) — This method is provded for you to assist in playing back your encoded message. If the dot parameter is true, it will play a short dot sound. If false, it will play a dash sound that is three times the length of the dot sound.

The MorseEncoder class will also contain a HashMapcalled MAP that will store the morse code information.

HashMap

Your HashMap class must implement the Map<K, V> interface to store each code in a key/value pair where the key is the character to be encoded and the value is the code associated with the key. Your implementation of the HashMap class must include implementations of the following methods (the remaining methods may throw an UnsupportedOperationException).

• clear()
• containsKey(Object key)
• get(Object key)
• isEmpty()
• put(K key, V value)
• remove(Object key)
• size()

The HashMap will consist of a set of HashMapEntry objects that map the key (character) to the corresponding symbol (Morse code). For example, one element in the table will store a mapping from A (the key) to .- (the value); Another element will store a mapping from B (the key) to -... (the value); Etc... The elements in the table will be sorted based on the keys. E.g., A, B, etc...

Your HashMap class must have an array of length 1024 for the hash table and be called entries. You must handle collisions using chaining. Every element of the array must be a list of Map.Entry<K, V> references. You can use the hash code of the key to determine the array index and store the entry in the associated list. Multiple keys may map to the same array index but keys may not be duplicated. You should not worry about tracking the collision rate or resizing the array.

Controller

Your Controller class will need to implement the Initializable interface and define at mimimmum the following functionality

• public void initialize(URL url, ResourceBundle resourceBundle) — Loads the Morse Code table once the GUI has been loaded.

• void open() — will ask the user for the text file to encode, display the message, encode the message, and display the encoded message.

• void save() — will ask the user for a filename, then save the encoded message as that file.

• void quit() — will exit the program

• void clear() — will clear the input and output text from the GUI.

• void about() — will generate a Dialog window with instructions on how to use the program

• void play() — will play the encoded message.

Additional details:

• The Morse code table must be read in from the morsecode.txt file in the data directory in the project.
• Your program must convert all characters to uppercase before looking up the corresponding Morse code.
• Your program must not encode characters that are not found in the lookup table. Any characters not in the dictionary must be displayed in an Alert window after encoding the message
• A space must be placed between each encoded character.
• There will be three menus in your GUI, File, Edit, and Help. Clear will be under the Edit menu and About will be under the Help menu.
• The Save and Play items will be disabled whenever there is no encoded message displayed.
• The menu items should be able to be activated either by selecting them with a mouse or using the following keyboard shortcuts.
  • meta-O: Open
  • meta-S: Save
  • meta-P: Play
  • meta-Q: Quit
  • meta-delete: Clear
  • meta-H: About
• When playing the message, use Thread.sleep(int milliseconds) to "play" silence between lines. You should play the code for spaces and newline characters, but also pause after each newline. Standard morse code uses the following timings:
  • Dot: 50 ms
  • Dash: 150 ms
  • Time between characters: 150 ms
  • Time between lines: 450 ms

Acknowledgements

This assignment was developed by Dr. Jay Urbain, Dr. Chris Taylor, Dr. RJ Nowling, and Prof. Sean Jones.