我想根据权重进行排序，但是compareto（）方法不起作用，但是当我在pojo中将权重类型更改为“integer”时，它就起作用了。有人能给我解释一下发生了什么事吗？请在下面找到我的代码

public class CollectionsDemo {
            public static void main(String[] args) {
                List<Apple> appleList = Arrays.asList(
                                            new Apple(10, "green"),
                                            new Apple(60, "green"),
                                            new Apple(150, "green"),
                                            new Apple(155, "red"),
                                            new Apple(175, "red"),
                                            new Apple(110, "green"));
            //sorting
            appleList.sort(new Comparator<Apple>() {
                @Override
                public int compare(Apple o1, Apple o2) {
                    return o1.getWeight().compareTo(o2.getWeight()); //compareTo() won't come up in suggestions
                    //return o1.getColor().compareTo(o2.getColor()); //this is working
                }
            });
        }
    }
        public class Apple {
            private int weight; //changing to Integer works
            private String color;
            //getters
            //setters
        }