为什么Java中的每个对象都隐含地扩展java.lang.Object类？ [英] Why does every object in Java implicitly extend java.lang.Object class?

问题描述

我已经在Java编程了很长一段时间，但是当我试图解释一个 java.lang.Object 类是给朋友时，我不能来不止一个简单的单行：

Java中的所有对象都扩展了 java.lang.Object 隐含




我不太确定为什么要这样做。

所以，我查看了 GrepCode ，希望能找到一些线索。现在我知道一个 java.lang.Object 是什么，它做什么，我想知道是否有任何具体的原因，为什么它是这样设计的。

我的问题仍然存在：为什么每个对象都要扩展 java.lang.Object ？

解决方案

我会说，原因是为了在Java中为所有对象提供一个通用的API来支持基本功能，如

• 同步 - 等待，通知， notifyAll


• 垃圾收集 - finalize


• 收藏支持 - hashCode ，等于


• 对象克隆 - 克隆

每个对象

• 有一个它属于的类 - getClass


• 可以将自己表示为一个字符串，因为我们是
  人类，可以读取字符串 - toString

I have been programming in Java for quite some time, but when I tried to explain what an java.lang.Object class is to a friend, I could not come up with more than a simple one-liner:

All objects in Java extend java.lang.Object implicitly

I was not quite sure why it should do so.

So, I looked upon the source code on GrepCode, hoping that I can find some clues. Now I know what a java.lang.Object is and what it does, I want to know if there was any specific reason as to why it was designed this way.

My question still prevails: why should every object extend java.lang.Object?

解决方案

I would say that the reason is to have a common API for all objects in java to supports basic functionality like

• synchronization - wait, notify, notifyAll
• garbage collection - finalize
• collection support - hashCode, equals
• object cloning - clone

And every object

• has a class it belongs to - getClass
• can represent itself as a string, because we are humans and can read strings - toString

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