How to generate 4 non-repeating numbers in java?

Question

Java

How to get 4 random numbers in a certain range, so that they don't repeat? I understand that the algorithm is simple, but the pot no longer cooks today, and the solution is needed today. Thank you.

Answer 1

Set<Integer> generated = new HashSet<Integer>();
Random r = new Random();
while (generated.size() < 4) {
generated.add(r.nextInt(10) + 1);
}

Answer 2

I don't own java stdlib, but in general I would generate one from the other

Answer 3

In short, a very crooked code (I wildly apologize), but the meaning is that there is a method with a match check.

public class Main {
    static int arraySize = 4;
    static int maxNumber = 10;
    static int array[];
    public static void main(String[] args) {
        Random random = new Random();
        array = new int[arraySize];
        for (int i = 0; i < arraySize; i++) {
            do {
                array[i]=random.nextInt(maxNumber);
            } while (coincidenceChecking(array[i],i));
        }
    }
    static boolean coincidenceChecking(int num, int numArray) {
        for (int i = 0; i < numArray; i++) {
            if (array[i] == num) return true;
        }
        return false;
    }
}