如何生成指定数量的随机数？

Question

Okay, I have a stack sized 24. I need to fill it with random numbers between 1-6. But the condition is every numbers amount should be the same. Like four times 1, four times 2, four times 3. At the end of the day I need to have stack sized 24 that contains random numbers between 1-6 but every numbers amount should be 4. I need to use only stack, I can't use arrays or array list. How can I do it?

 int counter1 = 0, counter2 = 0, counter3 = 0, counter4 = 0, counter5 = 0, counter6 = 0;
    while(!(ottf.isFull())) {
        int x = rnd.nextInt(6) + 1;
        if (x == 1)
            counter1++;
        else if (x == 2)
            counter2++;
        else if (x == 3)
            counter3++;
        else if (x == 4)
            counter4++;
        else if (x == 5)
            counter5++;
        else
            counter6++;

        if (counter1 <= 4 && counter2 <= 4 && counter3 <= 4 && counter4 <= 4 && counter5 <= 4 && counter6 <= 4)
            ottf.push(x);}

I've tried to do it with counters but i guess this won't fix my problem.

Answer 1

if (counter1 <= 4 && counter2 <= 4 && counter3 <= 4 && counter4 <= 4 && counter5 <= 4 && counter6 <= 4)

I guess this is wrong, because you use && which stops any number of being added if one of the counters are over 4.

Use this instead:

if (x == 1 && counter1 < 4)
        ottf.push(x);
        counter1++;

etc. Try debugging and post your result, if you have issues

Answer 2

Can you try this? I gave you the piece of code regarding your idea. it's shorter and cleaner.

//this array is for counting only. The output is also a stack.
int[] count = new int[6];

while(!ottf.isFull()) {
    int x = rnd.nextInt(6) + 1;
    if(count[x-1]>4) {
       continue;
    }
    count[x-1]++;

    if (count[x-1]<=4) {
      //push to stack
      ottf.push(x);
    }
}

Answer 3

Try this. It only uses Stack. No arrays and no lists.

        Stack<Integer> stack = new Stack<>();
        for (int i = 0; i < 24; i++) {
            stack.push((i%6)+1);
        }
        Collections.shuffle(stack);

        System.out.println(stack);

The output will always be different unless you seed shuffle. But here is one example.

[5, 2, 1, 6, 3, 4, 5, 1, 4, 3, 2, 6, 1, 4, 3, 6, 2, 5, 3, 2, 6, 5, 4, 1]

Answer 4

Such cases can be handled using switch...case in a better way.

Do it as follows:

import java.util.Collections;
import java.util.Random;
import java.util.Stack;

public class Main {
    public static void main(String[] args) {
        Random rnd = new Random();
        int counter1 = 0, counter2 = 0, counter3 = 0, counter4 = 0, counter5 = 0, counter6 = 0;
        Stack ottf = new Stack();
        do {
            int x = rnd.nextInt(6) + 1;
            switch (x) {
            case 1:
                if (counter1 < 4) {
                    ottf.push(x);
                    counter1++;
                }
                break;
            case 2:
                if (counter2 < 4) {
                    ottf.push(x);
                    counter2++;
                }
                break;
            case 3:
                if (counter3 < 4) {
                    ottf.push(x);
                    counter3++;
                }
                break;
            case 4:
                if (counter4 < 4) {
                    ottf.push(x);
                    counter4++;
                }
                break;
            case 5:
                if (counter5 < 4) {
                    ottf.push(x);
                    counter5++;
                }
                break;
            case 6:
                if (counter6 < 4) {
                    ottf.push(x);
                    counter6++;
                }
            }
        } while (ottf.size() < 24);
        Collections.sort(ottf);// Not required. Doing it just to validate the result quickly
        System.out.println(ottf);
    }
}

Output:

[1, 1, 1, 1, 2, 2, 2, 2, 3, 3, 3, 3, 4, 4, 4, 4, 5, 5, 5, 5, 6, 6, 6, 6]