How do I fix my random number while loop?

Question

What I need to do is make a number generator that stops when it generates 10 and shows how many attempts there was until 10 was reached. I also have to use only while loops for this. Here's my code now:

public static int RandomOccurrence()
{               
  int randNumber = (int)(Math.random()*20 + 1);
  int count = 0;

  while(randNumber != 11){
    System.out.println("The number generated is " + randNumber);
    count = count + 1;
  }
  return count;
}

and here's the function call:

int number = RandomOccurrence();
    System.out.println("It took " +number +" tries before 10 was generated");   
        
    System.out.println();
    System.out.println();

But when I run the code it prints "the number generated is 2" infinitely.

Answer 1

Here's a fixed version of your code, which mostly involves moving the line that gets a random number into the while loop:

public static int RandomOccurrence()
{
    int randNumber = 0;
    int count = 0;

    while(randNumber != 10){//I changed the 11 to 10 because you said you wanted to stop at 10
        randNumber = (int)(Math.random()*20 + 1);//added
        System.out.println("The number generated is " + randNumber);
        count = count + 1;
    }
    return count;
}

System.out.println(RandomOccurrence());

Sample result:

The number generated is 1
The number generated is 4
The number generated is 20
The number generated is 19
The number generated is 10
5

Answer 2

I really prefer to point the user towards the answers for homework problems instead of giving them code that works. Because we're trying to "teach a man to fish."

The problem with the original code is that it must generate another random number within the while loop. The simplest way to do this is to copy-and-paste the same function-call that you used to generate the first one.

PS: You'll very quickly now see that "there's more than one way to do it!"

Answer 3

you should update your random number every time the while loop gets executed: So randNumber = (int)(Math.random()*20 + 1); should be inside the loop

public static int RandomOccurrence(){               
    int count = 0;
    int randNumber = 0;

    while(randNumber != 11){
        randNumber = (int)(Math.random()*20 + 1);
        System.out.println("The number generated is " + randNumber);
        count = count + 1;
    }
    return count;
}

public static void main(String...args){
    int number = RandomOccurrence();
    System.out.println("It took " +number +" tries before 10 was generated");   
        
    System.out.println();
    System.out.println();
}

I hope I could help

Answer 4

Here's a 1-liner:

long count = IntStream.generate(() -> (int)(Math.random() * 20 + 1))
    .takeWhile(i -> i != 11).count();

See live demo .