Java KnowledgeTree

input.txt

Animal
dog

KnowledgeTree.java

import java.io.BufferedReader;
import java.io.FileReader;
import java.io.IOException;
import java.io.InputStreamReader;

public class KnowledgeTree {
	private String topicofthegame;
	private Node treebase;	
    
	public KnowledgeTree(BufferedReader file) throws IOException {
	    topicofthegame = file.readLine();
	    treebase = readTree(file);
	}
	
	private static BufferedReader userInput = new BufferedReader(new InputStreamReader(System.in));
	
	private static Node readTree(BufferedReader inputfile) throws IOException {
	  
		boolean isQuestion = false;
		String contents = inputfile.readLine();
    
			if (isQuestion) {
			
				Node No = readTree(inputfile);
				Node Yes = readTree(inputfile);
				return new Node(contents, No, Yes);
			}
			else
				return new Node(contents);
	}
	

	public void startTree() throws IOException {
	    Node currentsubject = treebase;
	    System.out.println("\nThink of an " + topicofthegame+" and I will guess");
	    if (! promptUserYesorNo("Did you think of an " + topicofthegame))
	    	return;
	    
	    		while (currentsubject.Question()) {
	    	
	    				if (promptUserYesorNo(currentsubject.getQuestion()))
	    					currentsubject = currentsubject.answerYes();
	    				else
	    					currentsubject = currentsubject.answerNo();
	    		}

	    		if (! promptUserYesorNo("Is it a " + currentsubject.getGuess())) {
	    
	    			String AnswerfromUser, QuestionfromUser;
		
	    			System.out.print("What type of " + topicofthegame + " Did you guess: "); 
	    			AnswerfromUser = userInput.readLine();
	    			System.out.println("Please type a question whose answer is Yes for an " + AnswerfromUser + " and No for a " + currentsubject.getGuess());
	    			QuestionfromUser = userInput.readLine();
	

	    			if (promptUserYesorNo("Is " + AnswerfromUser + " Your answer?"))
	    				currentsubject.Question(QuestionfromUser, new Node(currentsubject.getGuess()), new Node(AnswerfromUser));
	    			else
	    				currentsubject.Question(QuestionfromUser, new Node(AnswerfromUser), new Node(currentsubject.getGuess()));
	    		}
		}
	    
	
	private static boolean promptUserYesorNo(String question) throws IOException {
		
    	String answer;
    
    		do {	
    			System.out.print(question + "? ");
    			answer = userInput.readLine();

    			if (answer.equals("yes".substring(0, answer.length())))
    				return true;
    			else if (answer.equals("no".substring(0, answer.length())))
    				return false;
    			else
    				System.out.println("Please type only yes or no");
    		}
    		while (true);
	}
	
		public static void main(String[] args) throws IOException {
	    
			String filename = "P7Test.txt";
			BufferedReader Subjectinput = new BufferedReader(new FileReader(filename));
			KnowledgeTree Tree = new KnowledgeTree(Subjectinput);
			Subjectinput.close();	    
	    			do {
	    			Tree.startTree();
	    			}
	    			while (promptUserYesorNo("Do you want to continue"));
	    			  System.out.println("Thank you and Goodbye");
	    			  System.exit(0);    
		}
}

Node.java

public class Node {
		
		private Node leftyesChild, rightnoChild;	
	    private String contents;	
	    private boolean Question;
	    
	    	void Question(String question, Node No, Node Yes)
			{
				leftyesChild = Yes;
	    		rightnoChild = No;
	    		Question = true;
	    		contents = question;	
	    	}
		 
			Node(String question, Node No, Node Yes) 
			{
				this.leftyesChild = Yes;
				this.rightnoChild = No;
				Question = true;
				contents = question;	
			}		

			Node(String guess) 
			{ 
				leftyesChild = null;
				rightnoChild = null;
				Question = false;
				contents = guess;
			}

			boolean Question() 
			{ 
				return Question; 
			}

			String getQuestion() 
			{
				return contents;
			}
		
			Node answerYes() 
			{
				return leftyesChild; 
			}

			Node answerNo() 
			{
				return rightnoChild;
			}

			String getGuess()
			{ 
				return contents;
			}
			
	 }