Problem

Generate a program where the computer chooses a random number between 1 and 10 and the user is continuously asked to guess it until they are correct. Use the following guidelines in coming up with a solution:

• JOptionPane for input and output
• Math.random() for generating the random number
• While loop for continuously asking for a guess until right
• Boolean variable for indicating when the while loop is done

While and For Loops

Solution

To begin (after importing javax.swing.*) we're going to need 3 variables; int randNum, String guess, Boolean correct.

int randNum; //used to store the randNum we generate
String guess; //used to store the guess
boolean correct = false; //loop variable initialized to false meaning our guess is incorrect

To generate a random number between 1 and 10 we will need to use the following code.
Note: Math methods do not require an import statement.

//(int)(Math.random() * 10 generates a random number from 0 to 9
//to get a random number from 1 to 10 we need to add 1
randNum = (int)(Math.random() * 10) + 1;

To get a guess from the user we will need to prompt them using JOptionPane then convert it to an int. We will assume valid input from the user. After we check the guess we will print out a message indicating if the user is correct.

//get the guess from the user
guess = JOptionPane.showInputDialog("Enter a guess between 1 and 10:");
//ensure that the user entered something
if(guess != null)
{
    //parse the guess into an integer and compare it to the randNum
    //then print out a corresponding message
    if(Integer.parseInt(guess) == randNum)
    {
        //set correct to true so that we can exit the while loop
        correct = true;
        JOptionPane.showMessageDialog(null, "You are correct", "", JOptionPane.INFORMATION_MESSAGE);
    }
    else
    {
        JOptionPane.showMessageDialog(null, "You are incorrect", "", JOptionPane.INFORMATION_MESSAGE);
    }
}

To continuously ask the user for a guess till correct, we can put the previous code inside of a while loop.

//loop until correct changes to true
while(correct == false)
{
    //get the guess from the user
    guess = JOptionPane.showInputDialog("Enter a guess between 1 and 10:");
    //ensure that the user entered something
    if(guess != null)
    {
        //parse the guess into an integer and compare it to the randNum
        //then print out a corresponding message
        if(Integer.parseInt(guess) == randNum)
        {
            //set correct to true so that we can exit the while loop
            correct = true;
            JOptionPane.showMessageDialog(null, "You are correct", "", JOptionPane.INFORMATION_MESSAGE);
        }
        else
        {
            JOptionPane.showMessageDialog(null, "You are incorrect", "", JOptionPane.INFORMATION_MESSAGE);
        }
    }
}

For the final solution code you can look under the code heading.

Code

Solution Code

import java.lang.Math; //needed for Math.random
import javax.swing.JOptionPane; //needed for JOptionPane

public class GuessMyNumber
{
    public static void main(String [ ] args)
    {
        int randNum; //used to store the randNum we generate
        String guess; //used to store the guess
        boolean correct = false; //loop variable initialized to false meaning our guess is incorrect

        //(int)(Math.random() * 10 generates a random number from 0 to 9
        //to get a random number from 1 to 10 we need to add 1
        randNum = (int)(Math.random() * 10) + 1;
        
        while(correct == false)
        {
            //get the guess from the user
            guess = JOptionPane.showInputDialog("Enter a guess between 1 and 10:");
            //ensure that the user entered something
            if(guess != null)
            {
                //parse the guess into an integer and compare it to the randNum
                //then print out a corresponding message
                if(Integer.parseInt(guess) == randNum)
                {
                    //set correct to true so that we can exit the while loop
                    correct = true;
                    JOptionPane.showMessageDialog(null, "You are correct", "", JOptionPane.INFORMATION_MESSAGE);
                }
                else
                {
                    JOptionPane.showMessageDialog(null, "You are incorrect", "", JOptionPane.INFORMATION_MESSAGE);
                }
            }
        }
    }
}