Java "guessing number" game

Question

First, sorry, when I dont have the best English, its not my first language..

So, to the problem.. Ive got an exercise, that i have to develope a minigame, in which I have to think for a number between 1 and 1024. The program then have to ask if a number is littler, greater than or equal to the number, the user thinks of. But the computer is only allowed to ask 10 questions. However. I dont know, how to do this and i already did it for the last few days. I also didnt find anything for it in the internet. Here is the Code i have till yet:

package numberguessing;

import java.util.Scanner;

public class Numberguessing {

    public static void main(String[] args) {


        int av = 0;
        int rz;
        System.out.println("Please think for a number between 1 and 1024");

        //  1   2   3    4    5    6     7     8     9      10
        // 2   4   8   16   32   64   128   256   512   1024


        System.out.println("I will know your number after max 10 questions");
        System.out.println("I will name you a number");
        System.out.println("You have to say, if the number is littler, greater than or equal to your number");

        rz = a/2 ;
        System.out.println("Is your number littler, greater than or equal to " + rz +"?");

        Scanner sc = new Scanner(System.in);
        String an = sc.next();


        do{
            av++;
            if(an.equalsIgnoreCase("littler")) {
                rz = rz / 2 ;
                System.out.println("Is your number littler, greater than or equal to " + rz +"?");
                an = sc.next();
            } else if(an.equalsIgnoreCase("greater")){
                rz =  (rz + 1024) / 2 ;
                System.out.println("Is your number littler, greater than or equal to " + rz +"?");
                an  = sc.next();
            }  else if(an.equalsIgnoreCase("equal")) {
            } else {
                System.out.println("Error: The answer wasnt littler, greater or equal");
        }} while(!an.equalsIgnoreCase("equal"));


        System.out.println("I won the game after " + av + " tries");


        sc.close();
}
}

Answer 1

You could use AbstractList and Collections to perhaps make it a little easier to follow:

import java.util.AbstractList;
import java.util.Collections;
import java.util.Scanner;

public class Numberguessing {
  public static void main(String[] args) {
    System.out.println("Please think for a number between 1 and 1024 inclusive");
    System.out.println("I will know your number after max 10 questions!");
    System.out.println("I will guess your number!");
    System.out.println("After each guess, respond with littler, greater, or equal depending on my guess.");
    int result = Collections.binarySearch(new AbstractList<Integer>() {
      private final Scanner in = new Scanner(System.in);
      public int size() { return 1025; }
      public Integer get(int i) {
        System.out.printf("My guess is: %d. Is it littler, greater, or equal? ", 0 + i);
        String s = in.nextLine();
        assert s.length() > 0;
        switch (s.toLowerCase()) {
          case "greater":
            return -1;
          case "littler":
            return 1;
          case "equal":
            return 0;
        }
        return -1;
      }
    }, 0);

    if (result < 0) {
      System.out.println("That is impossible.");
    } else {
      System.out.printf("Your number is %d.\n", result);
    }
  }
}

Try it here!

Example usage where I choose to guess 513:

Please think for a number between 1 and 1024 inclusive
I will know your number after max 10 questions!
I will guess your number!
After each guess, respond with littler, greater, or equal depending on my guess.
My guess is: 512. Is it littler, greater, or equal?  greater
My guess is: 768. Is it littler, greater, or equal?  Littler
My guess is: 640. Is it littler, greater, or equal?  littler
My guess is: 576. Is it littler, greater, or equal?  littler
My guess is: 544. Is it littler, greater, or equal?  littler
My guess is: 528. Is it littler, greater, or equal?  littler
My guess is: 520. Is it littler, greater, or equal?  littler
My guess is: 516. Is it littler, greater, or equal?  littler
My guess is: 514. Is it littler, greater, or equal?  littler
My guess is: 513. Is it littler, greater, or equal?  EQUAL
Your number is 513.