没有可访问的封闭实例。必须使用类型为的封闭实例限定分配（例如x.new A（），其中x是的实例）[duplicate]

Question

我是编程新手，明年我将在大学学习它。在我的公共静态空虚主...我不能创建一个新的SimpleCircle。这个错误只发生在我的圆上。非常感谢你的帮助！：）

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());
    }
}

Answer 1

您将SimpleCircle类声明为TestSimpleCircle的内部类。您需要将其移动到单独的文件中，或者将其声明为

static class SimpleCircle