无法访问任何封闭实例。必须使用类型的封闭实例限定分配（例如 x.new A（），其中 x 是 的实例）

我是编程新手，明年我会在大学里学习。在我的公共静态虚空主...我无法创建新的 SimpleCircle。此错误仅发生在我的圈子上。非常感谢您的帮助！:)

public class TestSimpleCircle {

    class SimpleCircle {
        double radius;

        SimpleCircle(){
            radius = 1;
        }

        SimpleCircle(double newRadius){
            radius = newRadius;
        }

        double getArea() {
            return radius * radius * Math.PI;
        }

        double getPerimeter() {
            return 2 * radius * Math.PI;
        }

        void setRadius(double newRadius) {
            radius = newRadius;
        }
    }

    public static void main(String [] args) {
        SimpleCircle circle = new SimpleCircle();
        System.out.println("the area of the circle of radius "+circle.radius+" is "+circle.getArea());

        SimpleCircle circle2 = new SimpleCircle(25);
        System.out.println("the area of the circle of radius "+circle2.radius+" is "+circle2.getArea());

        SimpleCircle circle3 = new SimpleCircle(125);
        System.out.println("the area of the circle of radius "+circle3.radius+" is "+circle3.getArea());

        circle.radius = 100;
        System.out.println("The area of the circle of radius "+circle.radius+" is "+circle.getArea());
    }
}