1到49中，随机抽取6个数

        int n = 49;
        int k = 6;

        int[] number = new int[n];
        int[] result = new int[k];
        for(int i=0;i<number.length;i++){
            number[i] = i+1;
        }

        for(int i = 0;i<result.length;i++){
            int r = (int)(Math.random()*n);
            result[i] = number[r];
            number[r] = number[n-1];
            n--;
        }

        for (int j:result) {
            System.out.println(j);
        }