java - Java 在内存(或其他地方)中如何表示对象的结尾？

Question

比如你创建了两个对象

Circle circle1 = new Circle();
Circle circle2 = new Circle();

我了解到circle1(还有circle2)指向堆上内存中对象的起始位置。但是现在问题来了，它怎么知道什么时候结束？

我唯一能想到的是每个类都等于一个新声明的类型，Java 将每个类型占用的空间存储在其他地方，这样它就知道 circle1 等于内存中的 20 个字节。这样它就神奇地无法改变 circle2 的那个点后面的任何东西。这只是我的想象，希望能找到真正的答案。

Answer 1

对象在 JVM 堆中的表示取决于以下引自 this link 中提到的实现其中描述了 JVM 的结构:

The Java Virtual Machine assumes no particular type of automatic storage management system, and the storage management technique may be chosen according to the implementor's system requirements

同样来自该链接:

2.7. Representation of Objects

The Java Virtual Machine does not mandate any particular internal structure for objects.

In some of Oracle’s implementations of the Java Virtual Machine, a reference to a class instance is a pointer to a handle that is itself a pair of pointers: one to a table containing the methods of the object and a pointer to the Class object that represents the type of the object, and the other to the memory allocated from the heap for the object data.