在Java中创建对象时会发生什么？ [英] What occurs when object is created in Java?

问题描述

我的老师给了我一个问题：

My teacher gave me a question:

用Java创建对象时会发生什么。

"What occurs when objects are created in Java".

据我所知，在创建对象时会发生内存分配，变量初始化和构造函数方法调用。

To the best of my knowledge, memory allocation, variable initialization and constructor method invocation happen when an object is created.

但我的老师说我几乎是对的。除了内存堆之外，后来的两件事情是正确的。相反，他说内存分配发生了。我认为该对象存储在堆中，所以我的老师错了。你这么认为吗？

But my teacher said that I was almost right. The 2 later things are right, except memory heap. Instead, he said the memory allocation occurs. I think that object is stored in heap, so my teacher is wrong. Do you think so?

推荐答案

与往常一样，找到这类问题的解决方案的最佳位置是Java语言规范。

As always, the best place to find a solution for these kinds of questions is in the Java Language Specification.

具体来说，来自关于新实例创建的部分，可以理解这是创建新对象时的顺序，只要没有异常发生：

Specifically, from the section on new instance creation, it can be understood that this is the sequence when a new object is created, as long as no exceptions occur:

1. 已分配内存。


2. 字段初始化为默认值。


3. 的第一行选择的构造函数被调用，除非它是 Object 。第一行我指的是调用 super（）或 this（），或隐式调用 super（） 。


4. 实例初始化程序被执行，字段初始化为其请求的值（实际上字段初始化通常编译为实例初始化程序的内联部分）。


5. 执行其余的构造函数代码。

1. Memory is allocated.
2. Fields are initialized to their default values.
3. The "first line" of the chosen constructor is invoked, unless it's an Object. By first line I mean either explicit call to super() or this(), or an implicit call to super().
4. The instance initializer is executed and the fields are initialized to their requested values (actually field initialization is usually compiled as an inline part of the instance initializer).
5. The rest of the constructor code is executed.

现在，您的老师可能正在谈论内存分配作为一个实际的操作系统调用 - 在这种情况下，他是正确的，因为JVM管理自己的堆，因此Java内存分配不一定转换为操作系统内存分配电话（尽管可能）。

Now, it is possible that your teacher is talking about memory allocation as an actual operating system call - and in that case he's right in the sense that the JVM manages its own heap and thus a Java memory allocation does not necessarily translate to an OS memory allocation call (although it may).

这篇关于在Java中创建对象时会发生什么？的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！