Java出现No enclosing instance of type E is accessible. Must qualify the allocation with an enclosing

问题：No enclosing instance of type Three is accessible. Must qualify the allocation with an enclosing instance of type Three (e.g. x.new A() where x is an instance of Three).

代码：public class Three {


public static void main(String[] args) {
Person person=new Person();
System.out.println(person.name);
}

public class Person{
public  String name="Person";
int age=0;
}

public class Child extends Person{
public String grade;
}
}

原因：内部类是动态的，也就是开头以public class开头。而主程序是public static class main。在Java中，类中的静态方法不能直接调用动态方法。只有将某个内部类修饰为静态类，然后才能够在静态类中调用该类的成员变量与成员方法。所以在不做其他变动的情况下，最简单的解决办法是将public class改为public static class.