java - 使用 protected 构造函数实例化一个类

Question

public class MyTest {
    public static void main(String str[]){
        Info i=new Info();
        i.value=20;
        System.out.println("Integer value is :"+i.value);
    }
}
class Info {
    int value;
    protected Info(){
    System.out.println("Class with protected constructor");
    }
}

-->我遗漏了一些有关 protected 修饰符的内容，但无法弄清楚。 --> 直到现在我已经读到一个带有 protected 构造函数的类只能由它的子类实例化，而且在同一个包或不同的包中也是如此。那上面怎么给我这个输出:Class with protected constructor 整数值为:20

Answer 1

因为 MyTest 和 Info 这两个类都在同一个包中。

同一个包中的类可以毫无问题地访问 protected 成员

If the member or constructor is declared protected, then access is permitted only when one of the following is true:

• Access to the member or constructor occurs from within the package containing the class in which the protected member or constructor is
  declared.

检查 JLS 6.6.2