当实例变量作为arraylist存在时类的不变性 [英] immutability of a class when an instance variable present as arraylist

问题描述

我有一个不可变的类

假设我有一个类型为ArrayList的成员变量的getter方法。在这种情况下，当我获得对该变量的引用时，我可以添加或删除它中的元素。在这种情况下，不变性似乎被违反。

Suppose I have a getter method for a member variable of type ArrayList. In that case when I get a reference to that variable, I can add or remove an element from it. In that case immutability seems to get violated.

任何人都可以详细解释这个概念吗？

Can anyone explain this concept in details?

推荐答案

你确实是对的。违反了不变性。

You are indeed right. Immutability is violated.

要使类不可变，您需要确保其所有getter都返回其状态可能发生更改的任何类的安全副本。

To make a class immutable, you need to make sure that all of its getters return safe copies of any class whose state could otherwise change.

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