Thread: Java program to convert and compare integers

hey everyone i'm trying to create a program where you pick a number between naught and fifteen to match a randomly generated number. here's what i have so far.

/*
 * To change this template, choose Tools | Templates
 * and open the template in the editor.
 */
 
package numberchoice;
import java.io.*;
import java.util.*;
 
/**
 *
 * @author John
 */
public class Main {
 
    /**
     * @param args the command line arguments
     */
    public static void main(String[] args) {
        char Choice = 0;
        // TODO code application logic here
        log("Pick a number between 0 and 15");
        try{
            Choice = (char)System.in.read();
        }catch (IOException ioe){
            System.exit(1);
        }
        Random randomGenerator = new Random();
        int Random = randomGenerator.nextInt(16);
log("The Number is: "+Random);
if(Choice == Random){
    log("You have won!");
}else{
    log("You have lost.");
}
    }
     private static void log(String aMessage){
    System.out.println(aMessage);
  }
 
 
}

and here is the output i get

run:
Pick a number between 0 and 15
0
The Number is: 0
You have lost.
BUILD SUCCESSFUL (total time: 14 seconds)

could any body help me out with this?
cheers,
luke.

Hello luke.

Welcome to the Java Programming Forums

There are a few things wrong with your code.

For a start, you have declared the wrong variable type. If you are working with numbers then you need to use Integer (int). Char is for characters such as A, B, C etc.

I have rewritten this for you. Please take a look at my example:

import java.util.Scanner;
 
public class Luke {
 
    /**
     * JavaProgrammingForums.com
     */
    private static int random, guess;
 
    public static void main(String[] args) {
 
        Scanner sc = new Scanner(System.in);
        System.out.println("Enter a number between 0 - 15");
 
        random = (int)(Math.random() * 15);
        //System.out.println(random);
 
        try{
 
            while(sc.hasNext()){
 
                guess = sc.nextInt();
 
                if(guess > 15){
                    System.out.println("Your guess must be less than 15!");
                    System.out.println("Enter a number between 0 - 15");
                }
                else if(guess == random){
                    System.out.println("Congratulations! You guessed correctly.");
                    break;
                }
                else{
                    System.out.println("Wrong guess. Try again.");
                }
 
            }
 
        }catch(Exception e){
            System.out.println("You must enter an integer!");
            System.exit(0);
        }
 
    }
 
}

Hello luke, no problem.

Here is the Scanner class API

Scanner (Java 2 Platform SE 5.0)

Do you need to complete this without the use of the Scanner class or is my example OK?

Hmm this is strange. I compiled the code you submitted above and changed the char variables to int. The problem is, when using System.in.read(); for some reason, if Choice is set to integer, it prints out a different value than from what you input. For example:

import java.io.*;
import java.util.*;
 
/**
 * @author John
 */
public class Main {
 
    public static void main(String[] args) {
 
        int Choice = 0;
        Random randomGenerator = new Random();
        int Random = randomGenerator.nextInt(16);
        System.out.println(Random);
 
        log("Pick a number between 0 and 15");
 
        try {
            Choice = (int)System.in.read();
            System.out.println(Choice);
        } catch (IOException ioe) {
            System.exit(1);
        }
 
        if (Choice == Random) {
            log("You have won!");
        } else {
            log("The Number is: " + Random);
            log("You have lost.");
        }
    }
 
    private static void log(String aMessage) {
        System.out.println(aMessage);
    }
 
}

I have added code to print out the value of Choice once entered. If you enter 5, for some reason it prints out 53?!

But the problem still remains when we change the Choice variable back to char. It prints out a different value from what you enter.
This is why Choice never equals Random so we never get a positive result.

Yes I understand now. I have just done some reading on System.in.read(). I can't remember the last time I used this on it's own.

Learning Java - Chapter 9 : Java

We see that System.in is obviously an inelegant and inefficient way to carry out routine text input. We therefore normally wrap this input stream with classes that provide more powerful methods.

This is why I use the Scanner class...

I was just attempting to fix your original code but I have no idea how to get System.in.read() to output an inputted integer value. I have tried all kinds of conversions but for some reason it's got the better of me! I hope you are happy with my Scanner class solution and continue to use it into the future!