声明/初始化原语等于创建新对象

发布于 2024-09-02 15:59:59 字数 67 浏览 5 评论 0原文

声明/初始化原语与创建新对象相同吗？据我所知，当我们创建原语时，我们还为它们创建包装类。顺便说一句，我在java上实现。

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自此以后，行同陌路 2024-09-09 15:59:59

不，分配原始值不会创建任何对象。

您可能指的是这样一个事实：当在需要引用类型（也称为“对象”）的上下文中使用基元值时，它们可以自动装箱到相应的包装器中：

int i = 13;     // this line does not create an object
Integer i2 = i; // at this line 13 is auto-boxed into an Integer object

char c = 'x';   // again: no object created:
List<Character> l = new ArrayList<Character>();
l.add(c);       // c is auto-boxed into a Character object

另外，我将尝试描述声明和初始化之间的区别：

int i;          // an int-variable is declared
int j = 0;      // an int-variable is declared and initialized
i = 1;          // an int-variable is assigned a value, this is *not* initialization

变量在第一次创建时被“声明”（即指定变量的类型和名称）。 在声明期间被赋值时它就会被初始化。

No, assigning primitive values does not create any objects.

What you might be referring to is the fact that primitive values can be auto-boxed into the corresponding wrappers, when they are used in a context where a reference type (a.k.a "an object") is required:

int i = 13;     // this line does not create an object
Integer i2 = i; // at this line 13 is auto-boxed into an Integer object

char c = 'x';   // again: no object created:
List<Character> l = new ArrayList<Character>();
l.add(c);       // c is auto-boxed into a Character object

Also, I'll try to describe the difference between declare and initialize:

int i;          // an int-variable is declared
int j = 0;      // an int-variable is declared and initialized
i = 1;          // an int-variable is assigned a value, this is *not* initialization

A variable is "declared" when it is created for the first time (i.e. you specify the type and name of the variable). It is initialized when it's assigned a value during declaration.

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缘字诀 2024-09-09 15:59:59

不，声明和初始化原始变量不会创建对象。让我们采用一个具有两个整数值的类 - 一个使用包装类型，一个不使用。

public class Foo
{
    private int primitive = 10;
    private Integer wrapper = new Integer(10);
}

primitive 变量的值就是数字 10。wrapper 变量的值是一个引用一个 Integer 对象，该对象又包含数字 10。因此 Foo 的实例将保留 primitive 中的数字和 primitive 中的引用的状态代码>包装。

Java 中的所有基本类型都有包装类，但您不会自动使用它们。

No, declaring and initializing a primitive variable does not create an object. Let's take a class with two integer values - one using the wrapper type and one not.

public class Foo
{
    private int primitive = 10;
    private Integer wrapper = new Integer(10);
}

The value of the primitive variable is just the number 10. The value of the wrapper variable is a reference to an Integer object which in turn contains the number 10. So an instance of Foo would keep state for the number in primitive and the reference in wrapper.

There are wrapper classes for all primitive types in Java, but you don't use them automatically.

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