设计继承类 [英] Designing classes for inheritance

问题描述

我正在阅读J. Bloch的Effective Java，现在我正处于继承部分的设计课程中。他描述了所谓的自用模式，据我所知，我们不能在其他可覆盖的方法中使用可覆盖的方法。

I'm reading J. Bloch's Effective Java and now I'm at the designing class for inheritance section. He described the so called self-use pattern which, as far as I got stated that we must not use overridable methods within the other overridable methods.

所以我的问题是关于如何让客户了解自我使用。我们应该在 Javadocs 中明确提到它：

So my question is about how to make the client be aware about self-using. Should we mention it explicitly within Javadocs like that:

/**
* This class is self-use, thus it cannot be inherited.
*/

或者我们甚至应该拒绝的诱惑自用。

Or we should even refuse the temptation of the self-use.

示例代码：
我们应该如上所述记录该类，还是必须避免这种自我使用？

Sample code: Should we document the class as I described above or we must avoid such self-using?

public class MyClass{

    public void overrideMe(){ 
        //something
        ovMe(); 
    }

    public void ovMe(){
         //some staff
    }
}

推荐答案

如上所述，自我使用是指一个可覆盖的方法调用另一个可覆盖的方法。例如，当 AbstractList.addAll 调用 AbstractList.add 。

As you stated, self-use is when one overridable method calls another overridable method. For example, when AbstractList.addAll calls AbstractList.add.

确保任何扩展课程的人都知道这一点很重要。想象一下，你正在编写一个基于 AbstractList 的新列表实现 - 你需要知道是否需要覆盖 addAll 和添加，或者您是否只需要覆盖添加。

It's important to make sure that anyone extending the class knows this. Imagine you were writing a new list implementation based on AbstractList - you need to know whether you need to override both addAll and add, or whether you only need to override add.

自用就好了。 Joshua Bloch所说的是如果你使用它，你必须确保任何扩展课程的人知道它。

Self-use is fine. What Joshua Bloch says is that if you use it, you must make sure that anyone extending the class knows about it.

有几种方法满足这个建议：

There are several ways to meet this recommendation:

• 你可以简单地避免自用。


• 你可以制作一个所涉及的方法 final ，因此无法覆盖。


• 你可以让班级最终，因此无法扩展。


• 您可以在其Javadoc评论中描述该类的自用模式（满足让其他人知道的要求） 。

• You could simply avoid self-use.
• You could make one of the methods involved final, so it can't be overridden.
• You could make the class final, so it can't be extended.
• You could describe the class's self-use patterns in its Javadoc comment (meeting the requirement of letting other people know).

另外，为避免混淆，请注意 Java语言本身并不关心自我使用模式。编译器，JVM或任何其他软件也不是。此建议纯粹是为了帮助可能正在使用您的代码的程序员（包括您，6个月后）。

Also, to avoid possible confusion, note that the Java language itself does not care about self-use patterns. Nor do the compiler, the JVM, or any other piece of software. This recommendation is purely to assist programmers who might be working with your code (including you, 6 months later).

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