Building a lotto machine using java. Program Doesn't function if same number is chosen more then once

Question

I am trying to build a lotto machine using java. This is the code:

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

public class wissam {
    public static void main(String[] args) {    
        int counter = 0;    
        int[] lottoNumbers = new int[6];    
        for (int x = 0; x < lottoNumbers.length; x++) {    
                Random rand = new Random();    
                lottoNumbers[x] = rand.nextInt(42) + 1;    
        }    
        int[] userChoice = new int[6];    
        System.out.println("Enter a number");    
        Scanner scan = new Scanner(System.in);    
        userChoice[0] = scan.nextInt();    
        for (int y = 1; y < userChoice.length; y++) {    
                System.out.println("Enter another number");    
                userChoice[y] = scan.nextInt();    
        }    
        for (int x = 0; x < lottoNumbers.length; x++) {    
            System.out.print(lottoNumbers[x] + " ");    
        }    
        System.out.println("");    
        for (int z = 0; z < userChoice.length; z++) {    
            for (int a = 0; a < lottoNumbers.length; a++) {
                if (lottoNumbers[z] == userChoice[a]) {    
                    counter++;    
                    int b = lottoNumbers[z];    
                    System.out.print("The common numbers were" + b + "");    
                }    
            }    
        }    
        if (counter == 0) {    
            System.out.println("You are such a loser");                
        }    
    }                
}

It asks the user to input 6 numbers and works fine, as long as the user chooses 6 distinct numbers between 1 and 42.

I want to check if the user inputs distinct numbers that are between 1 and 42, and if they aren't I want to ask the user to change the number. How do I do that?

Have you tried anything yourself? Did you write that code yourself? — f1sh, May 09 '17 at 14:35
I think this question has essentially been answered here: http://stackoverflow.com/questions/3059333/validating-input-using-java-util-scanner. ---------- — J.P., May 09 '17 at 14:37

score 0 · Answer 1 · answered May 09 '17 at 14:43

0

I would not use an array. I would use a Set. It has the function 'contains'. So whenever the users gives another number, you can check if the Set so far already contains the number.

answered May 09 '17 at 14:43

GreyFairer

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I'll make sure to check and see if that works. Thanks for your answer – WissamM May 10 '17 at 17:57

score 0 · Answer 2 · answered May 09 '17 at 14:50

I would do it this way

public static void main(String[] args) {
  final ArrayList<Integer> userChoice = new ArrayList<>(6);

  // Scan numbers
  Scanner scan = new Scanner(System.in);
    while (userChoice.size() < 6) {
      System.out.println("Enter a number");
      int choice = scan.nextInt();

      if (choice < 1 || choice > 42) {
        System.out.println("Number not between 1 and 42");
        continue;
      }

      if (userChoice.contains(choice)) {
        System.out.println("Number already chosen");
        continue;
      }

      userChoice.add(choice);
    }

    System.out.println("You have chosen: " + userChoice);
}

Ousmane D. · Answer 3 · 2017-05-09T14:54:17.470

Considering that you're almost there, the simplest case would be to create nested loops and before you store the number, check that it's not already within the array.

for (int y = 1; y < userChoice.length; y++) {

     System.out.println("Enter another number");
     boolean flag = false;
     int result = scan.nextInt();

     if(result < 1 || result > 42){
        System.out.println("please enter a number between 1 - 42 inclusive");
        y--;
        continue;
     }

     for(int i = 1; i <  userChoice.length; i++){
        if(result == userChoice[i]){
           flag = true;
           break;
        }
     }

     if(flag){
        System.out.println("Enter a different number");
        y--;
     }else{
        userChoice[y] = result;
     }

}

Building a lotto machine using java. Program Doesn't function if same number is chosen more then once

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