Java生成N个不重复的随机数的三种方法总结

import java.util.HashSet;
import java.util.Random;
import java.util.Set;
public class RandomNumberGenerator {
    public static Set<Integer> generateRandomNumbers(int n, int max) {
        if (n > max) {
            throw new IllegalArgumentException("n must be less than or equal to max");
        }
        Set<Integer> set = new HashSet<>();
        Random random = new Random();
        while (set.size() < n) {
            int num = random.nextInt(max) + 1;
            set.add(num);
        }
        return set;
    }
    public static void main(String[] args) {
        Set<Integer> set = generateRandomNumbers(5, 100);
        System.out.println(set);
    }
}

import java.util.Arrays;
import java.util.Random;
public class RandomNumberGenerator {
    public static int[] generateRandomNumbers(int n, int max) {
        if (n > max) {
            throw new IllegalArgumentException("n must be less than or equal to max");
        }
        int[] arr = new int[n];
        Random random = new Random();
        for (int i = 0; i < n; i++) {
            int num;
            do {
                num = random.nextInt(max) + 1;
            } while (contains(arr, num));
            arr[i] = num;
        }
        return arr;
    }
    private static boolean contains(int[] arr, int num) {
        for (int i : arr) {
            if (i == num) {
                return true;
            }
        }
        return false;
    }
    public static void main(String[] args) {
        int[] arr = generateRandomNumbers(5, 100);
        System.out.println(Arrays.toString(arr));
    }
}

import java.util.Arrays;
import java.util.Random;
public class RandomNumberGenerator {
    public static int[] generateRandomNumbers(int n, int max) {
        if (n > max) {
            throw new IllegalArgumentException("n must be less than or equal to max");
        }
        int[] arr = new int[max];
        for (int i = 0; i < max; i++) {
            arr[i] = i + 1;
        }
        Random random = new Random();
        for (int i = max - 1; i >= max - n; i--) {
            int index = random.nextInt(i + 1);
            int temp = arr[index];
            arr[index] = arr[i];
            arr[i] = temp;
        }
        return Arrays.copyOfRange(arr, max - n, max);
    }
    public static void main(String[] args) {
        int[] arr = generateRandomNumbers(5, 100);
        System.out.println(Arrays.toString(arr));
    }
}