如何一个类有自己的类型的成员，不是这个无限递归？ [英] How can a class have a member of its own type, isn't this infinite recursion?

问题描述

假设我定义了一个类，该类的成员变量与自身类型相同。

Say I define a class that has as a member a variable of the same type as itself.

public class abc {
    private abc p;
}

这实际上是有效的，

为什么我认为它不应该：创建一个 abc 的实例，它包含一个< c $ c> abc ，其中包含 abc 类型的变量，其中包含 abc ，其中.....

Why I think it shouldn't: creating an instance of abc, it contains a variable of type abc, which contains a variable of type abc, which contains a variable of type abc, which .....

显然我错了，有人能告诉我如何？

Obviously I'm wrong, could someone enlighten me as to how?

推荐答案

你只声明变量而不创建它。尝试在声明或构造函数中创建它，并让我知道会发生什么：

You're only declaring the variable and not creating it. Try creating it at declaration or in the constructor and let me know what happens:

public class Abc {
   private Abc p = new Abc(); // have fun!

   public static void main(String[] args) {
      new Abc();
   }
}

顺便提一下，如果你不在类，而是在getter方法或构造函数参数中接受对它的引用，您的代码将正常工作。这是一些链接列表的工作原理。

Incidentally, if you don't create it in the class, but rather accept a reference to it in a getter method or a constructor parameter, your code will work just fine. This is how some linked lists work.

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