实例化值类型 [英] Instantiating a value type

问题描述

我在第一种情况下声明一个int类型的变量，在第二种情况下我实例化了相同的变量，以下是两种情况:

案例1:

int a;
a = 10;

现在我实例化一个int类型的变量

情况2:

int a = new int();
a = 10;



以上两种情况有什么区别，内部到底发生了什么.


问候
Chaithu

Hi,

I declare a variable of type int in the first case and in the second case i instantiate the same,Below are the 2 cases :

case1:

int a;
a=10;

Now I instantiate a variable of type int

Case 2:

int a =new int();
a=10;



what is the difference between the above two cases,what exactly happens internally.


Regards
Chaithu

推荐答案

我相信在情况1中，变量声明为没有值，然后分配为"10".
在情况2中，变量使用其默认值(为"0")声明，然后分配为"10".

但这只是我的2美分.

I believe that in case 1, the variable is declared without a value and then assigned ''10''.

In case 2 the variables is declared with it''s default value (which is ''0'') and then assigned ''10''.

But that''s just my 2 cents.

要解释您的问题，请看下面的示例.

To explain your question, look at the example below.

struct Person
{
    public Person(int age)
    {
        this.Age = age + 10;
    }
    public int Age;
}

然后像访问它一样

And then access it like

Person person =new Person();
person.Age = 10;

Person person1 = new Person(10);

您期望Person的年龄为10，但是Person1的值为20.使用new 关键字可以调用特定的构造函数.对于第二种情况，您要调用默认构造函数，该构造函数将0分配给变量，然后将其分配值.在第一种情况下，int会接受与值类型隐式兼容的值.

对于int，调用的两种方式是相同的，因为您只是使用默认的构造函数.

希望这会有所帮助.

注意:值类型与引用类型不同在上面的示例中，如果此人是class，则

Person1= Person; Person1.Age=30; then Person.Age also equals 30.但如果是值类型，则Person.Age将具有原始值.值类型存储在堆栈中，新变量将位于新的内存地址中.参考变量指针位于堆栈中，该指针指向堆中的地址.因此，两个变量可以在堆中保存一个公共地址.

祝你好运

What you expect Person''s age is 10, but Person1''s value will be 20. Using the new key word you can call a specific constructor. For your second case you are calling a default construtor which assign a 0 to the variable and then you are assigning value to it. In the first case the int will accept a compatible value which implicitly to the value type.

For the int, the both ways you are calling are same, because you are using simply a default constructor.

Hope this helps.

Note: value types are different from reference types In the above example if the person is a class then

Person1= Person; Person1.Age=30; then Person.Age also equals 30. But in case of value type Person.Age will have the original value. Value types stores on the stack and a new variable will be in a new memory address. Reference variable pointers are in the stack which points to an address in the heap. So two variable can hold a common address in the heap.

Good luck

查看此链接

http://www.coderanch.com/t/468841/java/java/difference-between-int-maxrows-Integer [ ^ ]

see this link

http://www.coderanch.com/t/468841/java/java/difference-between-int-maxrows-Integer[^]

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