Special Section: Challenging String-Manipulation Projects

(Project: A Spelling Checker) Many popular word-processing software packages have built-in spell checkers. In this project, you are asked to develop your own spell-checker utility. We make suggestions to help get you started. You should then consider adding more capabilities. Use a computerized dictionary (if you have access to one) as a source of words.

Why do we type so many words with incorrect spellings? In some cases, it is because we simply do not know the correct spelling, so we make a best guess. In some cases, it is because we transpose two letters (e.g., "defualt" instead of "default"). Sometimes we double-type a letter accidentally (e.g., "hanndy" instead of "handy"). Sometimes we type a nearby key instead of the one we intended (e.g., "biryhday" instead of "birthday"), and so on.

Design and implement a spell-checker application in Java. Your application should maintain an array wordList of strings. Enable the user to enter these strings. [Note: In Chapter 14, we have introduced file processing. With this capability, you can obtain the words for the spell checker from a computerized dictionary stored in a file.]

Your application should ask a user to enter a word. The application should then look up that word in the wordList array. If the word is in the array, your application should print "Word is spelled correctly." If the word is not in the array, your application should print "word is not spelled correctly." Then your application should try to locate other words in wordList that might be the word the user intended to type. For example, you can try all possible single transpositions of adjacent letters to discover that the word "default" is a direct match to a word in wordList. Of course, this implies that your application will check all other single transpositions, such as "edfault," "dfeault," "deafult," "defalut" and "defautl." When you find a new word that matches one in wordList, print it in a message, such as

Did you mean "default"?  

Implement other tests, such as replacing each double letter with a single letter, and any other tests you can develop to improve the value of your spell checker.

(Project: A Crossword Puzzle Generator) Most people have worked a crossword puzzle, but few have ever attempted to generate one. Generating a crossword puzzle is suggested here as a string-manipulation project requiring substantial sophistication and effort.

There are many issues the programmer must resolve to get even the simplest crossword-puzzle-generator application working. For example, how do you represent the grid of a crossword puzzle inside the computer? Should you use a series of strings or two-dimensional arrays?

The programmer needs a source of words (i.e., a computerized dictionary) that can be directly referenced by the application. In what form should these words be stored to facilitate the complex manipulations required by the application?

If you are really ambitious, you will want to generate the clues portion of the puzzle, in which the brief hints for each across word and each down word are printed. Merely printing a version of the blank puzzle itself is not a simple problem.