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java类的访问级别

package-private

在官方的指导中这样描述java类的访问级别:

At the top level—public, or package-private (no explicit modifier).

At the member level—public, private, protected, or package-private (no explicit modifier).

不知道package-private是什么,于是继续往下看,看到了这样的一段话:

A class may be declared with the modifier public, in which case that class is visible to all classes everywhere. If a class has no modifier (the default, also known as package-private), it is visible only within its own package (packages are named groups of related classes — you will learn about them in a later lesson.)

大概的意思是,当一个类没有加任何访问修饰符的时候,他的默认访问级别就是package-private,即对其所在包内的其他类是可见的,对包外的类是不可见的,也就是我们常说的package级别。

Access Levels

Modifier

Class Package Subclass World
public  Y Y Y Y
protected Y Y Y N
no modifier Y Y N N
private Y N N N

 




 

java类的访问级别