Random numbers

Sephiroth_dude

I have an arraylist of numbers, I want to add two random numbers from that list to two other lists, I have that working,it always gives me random numbers but the problem is the output is always like this, both indexes are the same number always

Computer list: [4, 4]

User list: [1, 1]

I would like the 4 and the 1 at index 1 to be different each time, so for example

Computer list: [4, 3]

User list: [1, 5]

here is the code

public static void main(String[] args){
         ArrayList<Integer> computerCards = new ArrayList<>();
        ArrayList<Integer> userCards = new ArrayList<>();
        int userChoice =0;
        int computerChoice =0;
        computerChoice = getRandomNumber().get(rand.nextInt(randomNumber.size()));
        userChoice = getRandomNumber().get(rand.nextInt(randomNumber.size()));
        for(int i = 0; i < 2; i++){
            computerCards.add(computerChoice);
            userCards.add(userChoice);
        }
         System.out.println("Computer list: " + computerCards);
         System.out.println("User list: " + userCards);
}
 
 
private static ArrayList<Integer> getRandomNumber(){
        ArrayList<Integer> randomNumber = new ArrayList<Integer>();
        randomNumber.add(1);
        randomNumber.add(2);
        randomNumber.add(3);
        randomNumber.add(4);
        randomNumber.add(5);
        randomNumber.add(6);
       return randomNumber;
    } 

How can I achieve this please ?

Idleater

How do I generate random integers within a specific range in Java?

awec

https://www.boards.ie/discussion/2058262949/random-numbers

Like this:

public static void main(String[] args){
        ArrayList<Integer> computerCards = new ArrayList<>();
        ArrayList<Integer> userCards = new ArrayList<>();

        // you only need to create 1 instance of this array. 
        ArrayList<Integer> numberSet = getRandomNumber();

        // you may as well just calculate the size once. 
        int numberSetSize = numberSet.size();

        for(int i = 0; i < 2; i++) {
            // you call rand.NextInt inside the array to get different values per-index
            computerCards.add(numberSet.get(rand.nextInt(numberSetSize)));
            userCards.add(numberSet.get(rand.nextInt(numberSetSize)));
        }

         System.out.println("Computer list: " + computerCards);
         System.out.println("User list: " + userCards);
}
 
 
private static ArrayList<Integer> getRandomNumber(){
        ArrayList<Integer> randomNumber = new ArrayList<Integer>();
        randomNumber.add(1);
        randomNumber.add(2);
        randomNumber.add(3);
        randomNumber.add(4);
        randomNumber.add(5);
        randomNumber.add(6);
       return randomNumber;
    } 

Sephiroth_dude

https://www.boards.ie/discussion/comment/119621241#Comment_119621241

@awec very helpful, thank you!