Mark Twain wrote it

MarkTwainWroteIt.java

import java.io.File;
import java.io.FileNotFoundException;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.HashMap;
import java.util.Map;
import java.util.Scanner;


public class MarkTwainWroteIt {
	
	public static void main(String[] args) throws FileNotFoundException {
		
		Scanner scan = new Scanner(System.in);
		
		HashMap<String, Double> wordFrequency = getWordFrequency(getFile("sample"), 0);
		HashMap<String, Double> wordFrequency2 = getWordFrequency(getFile("huckfinn") + getFile("tomsawyer"), 1);
		
		
		double totalDifference = 0, total = 0;
		
		for (Map.Entry <String, Double> pair : wordFrequency.entrySet()) {
			String word = pair.getKey();
			double freq1 = pair.getValue();
			if (wordFrequency2.containsKey(word)) {
				double freq2 = wordFrequency2.get(word);
				totalDifference = totalDifference + Math.abs(freq2 - freq1);
				total = total + 1;
			}
		}
		if (total > 0) {
			System.out.println("Average difference: " + (totalDifference * 100 / total) + "%");
		}
		else {
			System.out.println("No common difference.");
		}
	}

	private static HashMap<String, Double> getWordFrequency(String content, int smoothing) {
		String raw = removePunctuation(content);
		String[] words = raw.split(" ");
		
		HashMap<String, Integer> word = new HashMap<String, Integer> ();
		HashMap<String, Double> wordFrequency = new HashMap<String, Double> ();
		
		
		for (int i = 0 ; i < words.length ; i++) {
			if (word.containsKey(words[i])) {
				word.put(words[i], word.get(words[i]) + 1);
			}
			else {
				word.put(words[i], 1);
			}
		}
		double wordCount = words.length;
		
		for (Map.Entry <String, Integer> pair : word.entrySet()) {
			if (pair.getValue() > smoothing) {
				wordFrequency.put(pair.getKey(), pair.getValue() / wordCount);
			}
		}
		return wordFrequency;
	}

	private static String removePunctuation(String content) {
		content = content.replace('.', ' ');
		content = content.replace('!', ' ');
		content = content.replace(',', ' ');
		content = content.replace('?', ' ');
		content = content.replace('-', ' ');
		content = content.replace(';', ' ');
		content = content.replace(':', ' ');
		content = content.replace('"', ' ');
		content = content.replace('_', ' ');
		content = content.replace('*', ' ');
		content = content.replace('[', ' ');
		content = content.replace(']', ' ');
		
		content = content.replaceAll("--", " ");
		content = content.replaceAll("\\.\\.\\.", "");
		content = content.replaceAll("\\s+", " ");
		
		content = content.toLowerCase();
		content = content.trim();
		return content;
	}

	private static String getFile(String name) {
		// Make the file object and a scanner.
		File mt = new File(name);
		Scanner input;
		// Try initializing the scanner and reading from it.
		try {
			input = new Scanner(mt);
			// Make a string builder to assemble the file into a string.
			StringBuilder sb = new StringBuilder();
			while (input.hasNextLine()) {
				sb.append(input.nextLine());
				sb.append(" ");
				// sb.append("\n")
			}
			return sb.toString();
		} 
		// But if you can't find a file, return the empty string.
		catch (FileNotFoundException e) {
			return "";
		}
	}
	
	
	
}