什么是C ++的const成员函数的Java等价物？ [英] What is the Java equivalent of C++'s const member function?

问题描述

在C ++中，我可以定义一个 accessor 成员函数，该函数返回私有数据成员的值（或引用），这样调用者就无法以任何方式修改该私有数据成员。 / p>

有没有办法用Java做到这一点？

如果有，怎么做？

我知道 final 关键字，但AFAIK，当应用于方法时：

1. 防止覆盖/多态化
   子类中的方法。


2. 使该方法内联 - 能够。（见@Joachim Sauer的评论）

但它不会限制方法返回引用到一个数据成员，以便调用者不能修改它。

我是否忽略了一些明显的东西？

解决方案

您要么返回不可变的对象，或返回私有实例变量的副本。这样，对象的内部状态被保护免于修改，即：

  private MyMutableObject mutable = ... 
 
 public MyMutableObject getMutableObject（）{
返回new MyMutableObject（this.mutable）; 
} 
` 
  

In C++, I can define an accessor member function that returns the value of (or reference to) a private data member, such that the caller cannot modify that private data member in any way.

Is there a way to do this in Java?

If so, how?

I know about the final keyword but AFAIK, when applied to a method it:

1. Prevents overriding/polymorphing that method in a subclass.
2. Makes that method inline-able. (see comment by @Joachim Sauer below)

But it doesn't restrict the method from returning a reference to a data member so that it can't modified by the caller.

Have I overlooked something obvious?

解决方案

You either return an immutable object, or return a copy of the private instance variable. This way, the object's internal state is "protected" from modification, i.e.:

private MyMutableObject mutable = ...

public MyMutableObject getMutableObject() {
   return new MyMutableObject(this.mutable);
}
`

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