java - 初始化变量就是为这个变量 分配内存，这句话对不？

Question

Java程序中的引用变量并不需要进行所谓的初始化操作，需要进行的是引用变量所引用的对象。

Answer 1

Initialized variable points:

1. Declare variables

2. Assign a value to a variable

Allocating memory is also divided into:

• Allocate memory in the heap

• Allocate memory on the stack

So, this question is relatively general.
First of all, here’s a chestnut:

int a;//分配jvm中的栈内存，形成一个引用
a = 1;//分配jvm中的堆内存

Another example:

String str = new String(“hello”);

• str This reference is placed on the stack

• The object instance created by new is placed on the heap

• The literal value "hello" is placed in the static storage area

Continue with the chestnut above:

String str1 = str;//此时，str1也是一个引用，放在栈上。指向堆里的hello

If you want to know more, you can read one of my columns. At the beginning, we briefly talked about the Java Memory Model.

Answer 2

That’s not right.
int i; //At this time, space is allocated for variable i, and i has a value
i=1; //Assignment

Initialization is just giving a meaningful value to this variable.

Answer 3

Initializing a variable means allocating memory for this variable. Is this correct?

That’s not true, at least in C++.

According to my understanding, in C++, to use a variable, the following three steps are generally required:

1. Declaration
   "Declaration" can introduce identifiers used by variables, but it does not allocate memory space. For example, the identifier extern int i;，表示i will be an integer in the subsequent program.

2. definition
   In addition to introducing the identifier used by the variable like the declaration, "definition" will also allocate the corresponding space according to the type of the variable, but will not be initialized (more accurately, "default initialization" will be performed. see below). For example int i;，就定义了一个整型变量i and allocate space to it.

3. Initialization
   "Initialization" means assigning a value to a variable when it is defined. For example, int i = 1;，就定义了一个整型变量i and allocate space for it, and set its value to 1.

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A little explanation about the "default initialization" above:

"Default initialization" (default initialization) is simply a process. When using T x;定义变量时，如果T是一个类，就调用这个类的默认构造函数来初始化x，如果T is a built-in type, no initialization is performed. For more details, please refer to the regulations in the C++ standard.

Answer 4

At least call the constructor

Answer 5

Not entirely correct, static in C++ objects will not allocate memory first

Answer 6

It’s not right in Java,
Object o;//This also allocates memory, allocates the memory of the object o,
o = new Object(); //Initialization, referenced object

Answer 7

That’s wrong
Generally, space is allocated to a variable when it is defined, while initialization is to assign an initial value to this space, which is not necessary. The two are not equivalent

Answer 8

Incorrect. Generally speaking, initializing a variable is just to make the variable meaningful. If it is meaningful, you can perform related operations