ArrayList .clone（）方法

Question

我对Array列表中的克隆概念感到困惑。例如：

                            Balloon green = new Balloon("Green",new Address("greenState", "greencity"));
                            Balloon green2 = (Balloon)green.clone();
                            green.setColor("NewGreen");
                            System.out.println(green);
                            System.out.println(green2);//color not affected in copy as color is of String type.
                                                       //Immutable objects are not shallow copied.
                            green.getAddress().state="helloState";
                            System.out.println(green);
                            System.out.println(green2);//Address does get affected

                            Output:- 
                            Balloon[color = NewGreen Address = Address {state = greenState, city = greencity}]
                            Balloon[color = Green Address = Address {state = greenState, city = greencity}]
                            Balloon[color = NewGreen Address = Address {state = helloState, city = greencity}]
                            Balloon[color = Green Address = Address {state = helloState, city = greencity}]

所以我很清楚。但是现在让我们获取数组列表。

                            Balloon red = new Balloon("Red",new Address("redState", "redCity")); 
                            Balloon blue = new Balloon("Blue",new Address("blueState", "blueCity"));
                            Balloon yellow = new Balloon("yellow",new Address("yellowState", "yellowCity"));

                            ArrayList<Balloon> list = new ArrayList<>();
                            list.add(red);
                            list.add(blue);
                            list.add(yellow);
                            ArrayList<Balloon> listCopy = (ArrayList<Balloon>)list.clone();
                            Balloon green = new Balloon("Green",new Address("greenState", "greencity"));

                            list.get(1).setColor("color");

                            list.add(green);

                            Output:-
                            [Balloon[color = Red Address = Address {state = redState, city = redCity}], Balloon[color = color Address = Address {state = blueState, city = blueCity}], Balloon[color = yellow Address = Address {state = yellowState, city = yellowCity}], Balloon[color = Green Address = Address {state = greenState, city = greencity}]]
                            [Balloon[color = Red Address = Address {state = redState, city = redCity}], Balloon[color = color Address = Address {state = blueState, city = blueCity}], Balloon[color = yellow Address = Address {state = yellowState, city = yellowCity}]]

因此，在上面的输出中，更改列表中气球的颜色也会影响副本。但是添加新元素不会反映在副本中。

有人可以解释吗？谢谢！

Answer 1

[clone上的

ArrayList]不会执行深层复制，这意味着它不会复制其包含的内容，而只是复制对这些元素的引用。您仍然分别只有one个绿色，蓝色和黄色的气球。您有一个引用四个气球的列表，一个引用三个气球的列表，这些列表在它们包含多少元素方面彼此独立。但是他们当前指向to的实际气球是共享的。