java - protected 内部类不能从另一个包的子类访问

Question

我在 Java 中有以下代码:

package a;
public classs ClassInOtherPackage{
    protected void protectedMethod(){}
     protected class protectedInnerClass {}
}

package b;
import a.*;
public class MyClass extends ClassInOtherPackage{
  public MyClass(){
    MyClass x = new MyClass();
    x.protectedMethod();  //<-- This one ok
    //UPDATED: Declaration is ok
    MyClass.protectedInnerClass y; //<-- This one ok
    //UPDATED: Only when instantiated is not allowed, why?
    y = x.new protectedInnerClass(); //<-- Not allow when instantiated.
  }
}

引用Java文档:

"The protected modifier specifies that the member can only be accessed within its own package (as with package-private) and, in addition, by a subclass of its class in another package."

为什么我不能像上面那样实例化内部保护类？

Answer 1

在JLS 8.8.9

8.8.9. Default Constructor

... if the class is declared protected, then the default constructor is implicitly given the access modifier protected (§6.6); ...

所以隐式声明的构造函数是:

protected class protectedInnerClass {
    protected protectedInnerClass(){
        super();
    }
}

您的代码无法编译，因为构造函数不可访问。