Akinator like

AskGame

import java.io.BufferedReader;
import java.io.InputStreamReader;


public class Game {
  BufferedReader br = new BufferedReader(new InputStreamReader(System.in));

  public static void main(String[] argv) throws Exception {
    Game game = new Game();
    game.entry();
  }

  public void entry() throws Exception {
    Node root = new Branch("Is it an animal?", null);

    while (true) {
      System.out.println("new round");
      askQuestion(root);
    }
  }

  private void askQuestion(Node node) throws Exception {
    while (node != null) {
      node.ask();
      String replyString = br.readLine().toLowerCase();
      Node nextNode = node.reply(replyString);

      if (nextNode == node) {  // entity, guessing success
        break;
      } else if (nextNode == null) {
        // might be empty branch
        // or wrong entity
        if (node instanceof Branch) {
          System.out.println("I lose, please provide new entity");
          String input = br.readLine();
          if (replyString.equals("yes") || replyString.equals("y")) {
            ((Branch)node).yes = new Entity(input, node);
          } else {
            ((Branch)node).no = new Entity(input, node);
          }
        } else if (node instanceof Entity) {
          System.out.println("I lose, please provide [question],[entity],[yes/no], split by ','");
          String[] tokens = br.readLine().split(",");
          Branch newBranch = new Branch(tokens[0], node);
          Entity newEntity = new Entity(tokens[1], node);
          String yesNo = tokens[2];

          Branch parentNode = (Branch)(node.parent);
          if (parentNode.yes == node) {
            // entity is on yes branch
            parentNode.yes = newBranch;
          } else {
            // entity is on no branch
            parentNode.no = newBranch;
          }

          if (isYes(yesNo)) {
            newBranch.yes = newEntity;
            newBranch.no = node;
          } else {
            newBranch.yes = node;
            newBranch.no = newEntity;
          }
        }
        break;
      } else /* branching */ {
        node = nextNode;
      }
    }
  }

  private boolean isYes(String str) {
    return str.equals("yes") || str.equals("y");
  }
}

public abstract class Node {
  Node parent;

  public Node(Node parent) {
    this.parent = parent;
  }

  public abstract void ask() throws Exception;
  public abstract Node reply(String str) throws Exception;
}

public class Branch extends Node {
  String question;
  Node yes;
  Node no;

  public Branch(String question, Node parent) {
    super(parent);
    this.question = question;
  }

  @Override
  public void ask() throws Exception {
    System.out.println(question);
  }

  @Override
  public Node reply(String str){
    // go to branch
    if (str.equals("yes") || str.equals("y")) {
      return yes;
    } else {
      return no;
    }
  }
}

public class Entity extends Node {
  String name;

  public Entity(String name, Node parent) {
    super(parent);
    this.name = name;
  }

  @Override
  public void ask() throws Exception {
    System.out.println(String.format("It's %s", name));
  }

  @Override
  public Node reply(String str) {
    // failed on guessing
    if (!str.equals("yes")) {
      return null;
    } else {
      return this;
    }
  }
}