Exercise 2

In this exercise, you will write a spellchecker. The input to your program will be a single word, which you will compare against a dictionary of words. The output should all the words in the dictionary that are "close in spelling" to the input word. We will define close as follows: Words w₁ and w₂ are close in spelling if any one of the following is true:

The two words are exactly the same (of course).
w₁ and w₂ are of the same length and differ in only one letter. For example, "cat" and "cut", differ in only the second letter, as do "cat" and "eat". But "book" and "bulk" differ in at least two letters.
The lengths of w₁ and w₂ differ by 1 and the shorter one can be obtained from the longer by removing one letter. For example, in comparing "cat" and "scat", you can remove 's' from "scat" and get the other word. Similarly, in comparing "cart" and "cat", you can remove 'r' from the first one to get the second one. However, in comparing "cat" and "cake", removal of a letter from the longer one does not result in the shorter one.

To get started:

Download SpellChecker.java, in w which you will write all your code.
You will also need WordTool.java and the dictionary words.
Your code will start in the method findClosestWords(), which has this signature:
```
    static String[] findClosestWords (String inputWord, String[] words)
    
```
Thus, it takes in an input and a dictionary, and returns a list of words that match. If no words match, return null.
You will likely need to break up your code into many methods because otherwise your findClosestWords() might become too bulky.
It might be useful, for example, to write a method that simply counts the number "mismatched" characters given two words of equal length and then to use that.
When you examine SpellChecker, you will see some GUI code has been written for you.
- Initially, you will not need the GUI. Indeed, if you look at main, you will see that the GUI creation has been commented out:
```
    public static void main (String[] argv)
    {
	test ();
	//SpellChecker checker = new SpellChecker ();

    }
      
```
- Instead, there is a simple test to see if your code works, with output to the commandline.
- Later, when it's mostly working, you can un-comment the GUI and run that - it's more fun that way.
- You don't need to understand how the GUI part of the code works.

Developing your program:

Start by getting 'equal' words to work: that is, your code should match "cat" and "cat".
Next, get a single mismatched character to work, e.g., "cat" and "eat".
Then add the rest. In doing so, make sure you don't break what's already working. Be aggressive in "defensive debugging", that is, write debug println's as you go.
Provide your own tests, at least three of them.

Submission:

Submit your file SpellChecker.java using these submission instructions. Do NOT email your program.
Don't forget to email the TA your encryption key.

What else is due:

Read through the supplemental material for Module 1 and try to do the exercises therein. Do NOT submit these exercises.