【numbers】LotteryDrawing.java的问题.苦思冥想想不出来numbersr=...

LotteryDrawing.java的问题.苦思冥想想不出来numbers【r】 = numbers【n-1】；n--是怎么解释,Scanner in = new Scanner(System.in);System.out.print(How many numbers do you need to draw:);int k = in.nextInt();System.out.priint(How mang highest numbers do you need to draw: );int n = in .nextInt();int[] numbers = new int[n];for(int i = 0 ; i { int[i] = i +1;//用1,2,3.n来填满数组；}int[] result = new int[k];for(int i = 0 ; i {int r = (int)(Math.random()*n);result[i] = numbers[r];//用随机生成的数值作为下标r,进行r+1运算后赋给result[i];numbers[r] = numbers[n-1];//为了防止出现相同的随机值!这里我就看不懂了.什么意思啊n--;//为了防止出现相同的随机值!这里我就看不懂了.什么意思啊}