我正在看这个程序，删除两个随机对象在同一时间从一个袋子。在袋子里有两种不同颜色的物体，根据物体的颜色，会发生不同的事情。我现在取随机值的方法是：

while (bag.size() > 1) {
            count++;
            int select1 = rnd.nextInt(bag.size());
            Balls indexPos1 = bag.get(select1);
            int select2 = rnd.nextInt(bag.size());
            Balls indexPos2 = bag.get(select2);
            System.out.println(select1);
            System.out.println(select2);

但在程序结束时，如果它碰巧采取了同一对象的索引，那么袋内的颜色变化是错误的，错误的结果打印。我将粘贴到循环的其余部分。

int count = 0;
        Random rnd = new Random();
// Depending on what colour the balls are either black ball is placed or white.
        while (bag.size() > 1) {
            count++;
            int select1 = rnd.nextInt(bag.size());
            Balls indexPos1 = bag.get(select1);
            int select2 = rnd.nextInt(bag.size());
            Balls indexPos2 = bag.get(select2);
            System.out.println(select1);
            System.out.println(select2);
            if (bag.size() != 1) {
                System.out.println(bag);
                System.out.println("Printing size: " + bag.size());
                if (bag.get(select1).equals(blackBalls) && indexPos2.equals(blackBalls)) {
                    System.out.println("Both balls are black.");
                    System.out.println("Removing black ball");
                    bag.add(blackBalls);
                    bag.remove(blackBalls);
                    bag.remove(blackBalls);
                    continue;
                }if (indexPos1.equals(whiteBalls) && indexPos2.equals(whiteBalls)) {
                    System.out.println("both Balls are white");
                    bag.add(blackBalls);
                    bag.remove(whiteBalls);
                    bag.remove(whiteBalls);
                    System.out.println("Removing 2 white balls. adding black.");
                    continue;
                }if (indexPos1.equals(whiteBalls) && indexPos2.equals(blackBalls) || indexPos1.equals(blackBalls) && indexPos2.equals(whiteBalls)) {
                    bag.add(whiteBalls);
                    bag.remove(select1);
                    bag.remove(select2);
                    System.out.println("Both balls are different.");
                    System.out.println("Removing white ball");
                }
            }
        }

我不知道如何从一个数组中随机抽取两个对象，所以它不会选择同一个对象两次。任何帮助或反馈都将不胜感激。