How to generate n different random numbers within a specified interval in java

Implementation method:

First define an array with a length of n, and then start using a while loop to generate random numbers to assign values ​​to the array. Before assigning values, you need to traverse the array. Existing values, if the values ​​are equal, regenerate random numbers without assigning values, and loop until all defined arrays are assigned.

Examples are as follows:

 /**
    * 功能：产生min-max中的n个不重复的随机数
    * 
    * min:产生随机数的其实位置
    * mab：产生随机数的最大位置
    * n: 所要产生多少个随机数
    *
    */
    public static int[] randomNumber(int min,int max,int n){
        //判断是否已经达到索要输出随机数的个数
        if(n>(max-min+1) || max <min){
            return null;
        }
        int[] result = new int[n]; //用于存放结果的数组

        int count = 0;
        while(count <n){
            int num = (int)(Math.random()*(max-min))+min;
            boolean flag = true;
            for(int j=0;j<count;j++){
                if(num == result[j]){
                    flag = false;
                    break;
                }
            }
            if(flag){
                result[count] = num;
                count++;
            }
        }
        return result;
    }

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Using the characteristics of Set, elements cannot be repeated

/**
     * 功能：随机指定范围内N个不重复的数
     * 
     * @param min 指定范围最小值
     * @param max 指定范围最大值
     * @param n 随机数个数
     */
    public static int[] randomSet(int min, int max, int n) {
        Set<Integer> set = new HashSet<Integer>();
        int[] array = new int[n];
        for (; true;) {
            // 调用Math.random()方法
            int num = (int) (Math.random() * (max - min)) + min;

            // 将不同的数存入HashSet中
            set.add(num);
            // 如果存入的数小于指定生成的个数，则调用递归再生成剩余个数的随机数，如此循环，直到达到指定大小
            if (set.size() >= n) {
                break;
            }
        }
        int i = 0;
        for (int a : set) {
            array[i] = a;
            i++;
        }
        return array;
    }

First put the generated random number into the set, and then determine the size of the set. If it does not exceed the required length, continue the loop. If it has exceeded, jump out of the loop and convert the set into an array.

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