RandomSentenceGenerator.java

/*
 * Author: cbedford
 * Date: 10/27/13
 * Time: 11:25 PM
 */

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.util.Hashtable;
import java.util.Random;
import java.util.Vector;

/*  not currently used */

public class RandomSentenceGenerator {

	// Hashmap
	public static Hashtable<String, Vector<String>> markovChain = new Hashtable<String, Vector<String>>();
	static Random rnd = new Random();

    private static String[] sentences = new String[]{
            "one king took the fox over the car.",
            "two queens bent the fox under the bed.",
            "four bears mined the pig into the house.",
            "Joe goats rolled the boat over the lodge.",
    };


    RandomSentenceGenerator() {
        // Create the first two entries (k:_start, k:_end)
        markovChain.put("_start", new Vector<String>());
        markovChain.put("_end", new Vector<String>());
    }

    String next() {
        int index = Math.abs(rnd.nextInt() % sentences.length);
        addWords(sentences[index]);
        return generateSentence();
    }


	/*
	 * Main constructor
	 */
	public static void main(String[] args) throws IOException {
        RandomSentenceGenerator generator = new RandomSentenceGenerator();

        while(true) {
            System.out.println("sentence: " + generator.next());
        }
	}

	/*
	 * Add words
	 */
	public static void addWords(String phrase) {
		// put each word into an array
		String[] words = phrase.split(" ");

		// Loop through each word, check if it's already added
		// if its added, then get the suffix vector and add the word
		// if it hasn't been added then add the word to the list
		// if its the first or last word then select the _start / _end key

		for (int i=0; i<words.length; i++) {

			// Add the start and end words to their own
			if (i == 0) {
				Vector<String> startWords = markovChain.get("_start");
				startWords.add(words[i]);

				Vector<String> suffix = markovChain.get(words[i]);
				if (suffix == null) {
					suffix = new Vector<String>();
					suffix.add(words[i+1]);
					markovChain.put(words[i], suffix);
				}

			} else if (i == words.length-1) {
				Vector<String> endWords = markovChain.get("_end");
				endWords.add(words[i]);

			} else {
				Vector<String> suffix = markovChain.get(words[i]);
				if (suffix == null) {
					suffix = new Vector<String>();
					suffix.add(words[i+1]);
					markovChain.put(words[i], suffix);
				} else {
					suffix.add(words[i+1]);
					markovChain.put(words[i], suffix);
				}
			}
		}
	}


	/*
	 * Generate a markov phrase
	 */
	public static String generateSentence() {

		// Vector to hold the phrase
		Vector<String> newPhrase = new Vector<String>();

		// String for the next word
		String nextWord = "";

		// Select the first word
		Vector<String> startWords = markovChain.get("_start");
		int startWordsLen = startWords.size();
		nextWord = startWords.get(rnd.nextInt(startWordsLen));
		newPhrase.add(nextWord);

		// Keep looping through the words until we've reached the end
		while (nextWord.charAt(nextWord.length()-1) != '.') {
			Vector<String> wordSelection = markovChain.get(nextWord);
			int wordSelectionLen = wordSelection.size();
			nextWord = wordSelection.get(rnd.nextInt(wordSelectionLen));
			newPhrase.add(nextWord);
		}

        String retval = newPhrase.toString().replaceAll(",", "");
        return retval;
	}
}