Question

So I have to create three random numbers using the Math.random(); method then use a for loop to output each number by itself and then using a concatenate to make them into a string. It’s for my assignment. I’ve done everything else. I could do it a different way but it requires a for loop. I can’t use the Random class. I have not learned it in my course, therefore it can’t be applied.

public class Lottery
{
    public static void main(String[] args)
    {
        //declare and initialized variables and objects
        Scanner input = new Scanner(System.in);



        //Identify the repeated steps and use a for loop structure


        for(int i=0; i < 3; i++) 
        {
            double lotto = Math.random(); 
            int lotteryNumberDigit = (int)(lotto*10);

           String lotteryNumberString = Integer.toString(lotteryNumberDigit);

        }



            String firstNumber = lotteryNumberString.substring(0,0);
            String secondNumber = lotteryNumberString.substring(1,1);
            String thirdNumber = lotteryNumberString.substring(2,2);

            String firstTwoWinner = firstNumber + secondNumber;
            String lastTwoWinner = secondNumber + thirdNumber;
            String allNumbersWinner = firstNumber + secondNumber + thirdNumber;

            System.out.println("Please enter your three numbers (e.g. 123): ");

            String userInput = input.next();

             if(userInput.substring(0,2).equals(firstTwoWinner))

        {
            System.out.println("Winner: " + allNumbersWinner );

            System.out.println("Congratulations, the front pair matched.");
        }

        else if (userInput.substring(1,3).equals(lastTwoWinner))
        {
             System.out.println("Winner: " + allNumbersWinner );

             System.out.println("Congratulations, the end pair matched.");
        }

        else if (userInput.equals(allNumbersWinner))
        {
             System.out.println("Winner: " + allNumbersWinner );

             System.out.println("Congratulations, both pairs matched.");
        }

        else
        {
             System.out.println("Winner: " + allNumbersWinner );

             System.out.println("Sorry, no matches. You only had one chance out of 100 to win anyway.");
        }



    }
}

I had to take out the arrays because my teacher said it was not expectable until the next chapter.

Answer 1

You can simply write below to print the 3 digit number.

    Random random = new Random();
    for(int i=0; i < 3; i++){
        int randomNumber = random.nextInt(10);
        System.out.print(randomNumber);
    }
        System.out.println();

Note: By using print method, you will print the three digits next to each other.

Alternatively you can do below:

    String newConcatNumString = "";
    Random random = new Random();
    for(int i=0; i < 3; i++){
       newConcatNumString  = newConcatNumString +random.nextInt(10);
    }
    System.out.println(newConcatNumString);

If you want to get the number from string, you can simply do:

    int concatenatedValue = Integer.parseInt(newConcatNumString);

EDIT:
If you don’t want to use Random class, do the below(updating first example only. Same can be applied into second as well):

    for(int i=0; i < 3; i++){
        int lotteryNumberDigit = (int)(Math.random()*10);
        System.out.print(lotteryNumberDigit);
    }
    System.out.println();

Edit: for you next problem, define an int[] in the beginning and store the values in the array for later use of comparison. Updated code snippet as below:

    int[] generatedNumbers = new int[3];
    for(int i=0; i < 3; i++){
        int lotteryNumberDigit = (int)(Math.random()*10);
                    generatedNumbers[i] = lotteryNumberDigit;
        System.out.print(lotteryNumberDigit);
    }
    System.out.println();

After the above loop, generatedNumbers will contain all three digits as separate entry in the array. Your comparison code can be as below:

  System.out.println("Please enter your three numbers, one digit at a time): ");
  for(int i=0; i<3; i++){
    int userInput = input.next();
    if(userInput == generatedNumbers[i]){
        System.out.println("Your digit "+i+" is correct");
    }else{
        System.out.println("Your digit "+i+" is incorrect");
    }
  }

EDIT:
Please do the comparison as below:

    if (userInput.equals(allNumbersWinner)) {
         System.out.println("Winner: " + allNumbersWinner );
         System.out.println("Congratulations, both pairs matched.");
    }else if(userInput.substring(0,2).equals(firstTwoWinner )) {
        System.out.println("Winner: " + allNumbersWinner);
        System.out.println("Congratulations, the front pair matched.");
    }else if (userInput.substring(1,3).equals(lastTwoWinner)) {
         System.out.println("Winner: " + allNumbersWinner );
         System.out.println("Congratulations, the end pair matched.");
    }else {
         System.out.println("Winner: " + allNumbersWinner );
         System.out.println("Sorry, no matches. You only had one chance out of 100 to win anyway.");
    }