# Guess a random number between a selected interval

Posted on

Problem

My project for my class is to create a Java-based game where the user must enter a number between 1-20 and a number between 250 and 300. The computer randomly chooses a number between those 2 numbers. Then the user has 10 guesses to correctly guess what number the computer is “thinking of.”

There is a catch, though. We cannot use `while` loops, only `if` and `else-if` statements. I have started this code and was wondering if I’m on the right track. Please point out anything that might help me!

``````package guessthenumber;

import java.util.Scanner;
import java.util.Random;

public class GuessTheNumber {

public static void main(String[] args)
{
int lowBoundary, highBoundary, secretNumber, boundaryDifference,
g1, g2, g3, g4, g5, g6, g7, g8,
g9, g10;
//g1, g2,... = guess 1, guess2,...

Scanner keyboard = new Scanner(System.in);

System.out.println("Can you guess the number I'm thinking of?nLet's "
+ "see if you can guess the right number within 10 guesses.nn"
+ "First please enter a number between 1 and 20.");
lowBoundary = keyboard.nextInt();

System.out.println("Excellent! Next enter a number between 250 and "
+ "350.");
highBoundary = keyboard.nextInt();

boundaryDifference = highBoundary - lowBoundary;
Random randomNumber = new Random();
secretNumber = randomNumber.nextInt(boundaryDifference) + lowBoundary;

System.out.println("The secret number has been chosen. Now you must "
+ "guessnthe secret number within 10 guesses or else you lose."
+ "n(Hint: The secret number is between " + lowBoundary +
" and " + highBoundary + ".)");
g1 = keyboard.nextInt();

if (g1 == secretNumber) {
System.out.println("CONGRATULATIONS! YOU'VE CORRECTLY GUESSEDnTHE"
+ "SECRET NUMBER ON YOUR FIRST GUESS!!");
}

else if (g1 < secretNumber) {
System.out.println("Higher than " + g1 + ". Guess again!");
g2 = keyboard.nextInt();

{
if (g2 == secretNumber) {
System.out.println("Awesome! You've correctly guessednthe"
+ "secret number in 2 guesses!");
}

else if (g2 < secretNumber) {
System.out.println("Higher than " + g2 + ". Guess again!");
g3 = keyboard.nextInt();

if (g3 == secretNumber) {
System.out.println("Great job! You've correctly guessedn"
+ "the secert number in 3 guesses!");
}
else if (g3 < secretNumber) {
System.out.println("Higher than " + g3 + ". Guess again!");
g4 = keyboard.nextInt();

if (g4 == secretNumber) {
System.out.println("Good job! You've correctly guessednthe"
+ " secret number in 4 guesses!");
}

else if (g4 < secretNumber) {
System.out.println("Higher than " + g4 + ". Guess again!");
g5 = keyboard.nextInt();

if (g5 == secretNumber) {
+ " secret number in 5 guesses!");
}

else if (g4 > secretNumber) {
System.out.println("Lower than " + g4 + ". Guess again!");
}
}
}

else if (g3 > secretNumber) {
System.out.println("Lower than " + g3 + ". Guess again!");
}
}

else if (g2 > secretNumber) {
System.out.println("Lower than " + g2 + ". Guess again!"
);
g3 = keyboard.nextInt();
}
}
}

else if (g1 > secretNumber) {
System.out.println("Lower than" + g1 + ". Guess again!");

{

}
}
}
}
``````

Solution

I’m guessing you’re not allowed to use any kind of loop, because then you could just use a for-loop.

Anyhow, I would suggest you encapsulate more of your code in methods. Think about what kind of operations you use repeatedly.

Also, you don’t need multiple guessing variables (g1, g2, g3, … , g10); you can make do with one.

Now to solve the main problem. I would suggest using a recursive method (a method that calls for itself). It can very well act as a loop and you could, for example, count the guesses with it among other things.

Here’s an example of a recursive method that returns the sum of all integers from 1 up to a given number:

``````public static int sumIntegers(int number){
if (number == 1)
return number;
return number + sumIntegers(number - 1);
}
``````

If you would call this method like this:

``````sumIntegers(5);
``````

You would get:
5 + 4 + 3 + 2 + 1 = 15

Hope it helps!

This code is somewhat broken (slightly):

``````    boundaryDifference = highBoundary - lowBoundary;
Random randomNumber = new Random();
secretNumber = randomNumber.nextInt(boundaryDifference) + lowBoundary;
``````

This is one of the most common duplicate problems on StackOverflow, and it’s a lesson you should just learn….

The above code will never produce the value ‘highBoundary`.

This is because `nextInt(boundaryDifference)` produces a result from 0 to `boundaryDistance` excluding `boundaryDistance`.

The right way to get a random number from a given range including both limits of the range is:

`````` int val = min + randomNumber.nextInt((max - min) + 1);
``````

Never forget the `+1`