Purposes:

• To familiarize you with BNF
• To give you some initial experience with recursion

General idea

Write a text file containing BNF grammar for English sentences. Here is an example you can start with, but you should either write your own, or "improve" this one. In either case, replace the vocabulary items (the "terminals") with your own vocabulary items.

Read in your BNF grammar and use it to generate about twenty random sentences.

Specifics

Write a main class SentenceGenerator that does the following:

• Uses a JFileChooser to prompt the user for a file containing the BNF grammar rules.
• Reads in the BNF grammar and stores it in a data structure as described below and in this lecture.
• Prints out the grammar.
• Generates and prints about twenty random sentences, one per line.
  • Print it "nicely": Capitalize the first word of the sentence and end it with a period.

You should have the following classes and their constructors and methods:

• public class SentenceGenerator
  • public static void main(String[] args)
  • A method to read in a grammar
  • List<String> generate(String term)
    • Expands the given term into a List of terminals. If the given term is already a terminal, returns a List containing this single term. This method is to be written as a recursive method.
  • A method to print out a List<String> as a sentence
  • Any other methods you need
    
    
• public class Grammar
  • Grammar() // constructor
  • public void addRule(String ruleText) throws IllegalArgumentException
  • public Definitions getDefinitions(String nonterminal)
  • public void print() // prints the grammar neatly, on multiple lines


• class Definitions extends ArrayList<SingleDefinition>
  • public String toString() // returns a single line


• class SingleDefinition extends ArrayList<String>
  • public String toString() // returns a single line


• public class GrammarTest extends TestCase
  • Test addRule. Remember to test whether addRule throws an IllegalArgumentException for some obvious cases of malformed BNF grammar rules.
  • Test getDefinitions.
  • Do not test print. You also don't need to test the Grammar constructor, since all it does is create a Map<String, Definitions>.
    
    
• public class DefinitionsTest extends TestCase
• public class SingleDefinitionTest extends TestCase
  • For both of these, test your toString method. The line returned by toString should be legal BNF.

Notes

You do not need to create a GUI for this program (although you may if you wish). If you do, SentenceGenerator should extend JFrame.

Your BNF rules should be kept in a Map<String, Definitions> in the SentenceGenerator Grammar class.

All non-private elements should have a well-written Javadoc comment. Remember that a Javadoc comment is supposed to tell the user everything s/he needs to know in order to use that element.

It is possible to write the generate method as an iteration rather than as a recursion. Don't! Part of the purpose of this assignment is to get you familiar with recursion.

Generate the Javadoc and look it over before you turn in your program.

Provided code

BnfTokenizer.java (use this tokenizer when you read in the grammar) and BnfTokenizerTest.java.

Due date

Zip up and turn in your complete project, including all test files and the generated Javadoc, via Blackboard, before midnight, Tuesday January 23.