我想处理从 Circle.getArea() 方法使用aspectj。
形状.java

package Shapes;

    public class Circle {
        private double radius;
        public Circle(double radius) {
               this.radius = radius;
        }
        public double getPerimeter(){
               return 2 * Math.PI * this.radius;
        }
        public double getArea(){
            return Math.PI * this.radius * this.radius;
        }
    }

矩形.java

package Shapes;

    public class Rectangle {
        private double width, height;
        public Rectangle(double width, double height) {
             this.width = width;
             this.height = height;
        }
        public double getPerimeter() {
               return 2 * (this.width + this.height);
        }
        public double getArea() {
               return this.width * this.height;
        }
    }

圆圈.java

package Shapes;

    public class Circle {
        private double radius;
        public Circle(double radius) {
            this.radius = radius;
        }
        public double getPerimeter() {
            return 2 * Math.PI * this.radius;
        }
        public double getArea() {
            throw new RuntimeException("Oops, I don't know how to calculate this :(");
        }
    }

主.java

package Shapes;

    public class Main {

        public static void main(String[] args) {
            try {
                Shape s;
                s = (Shape) new Rectangle(2, 10);
                System.out.println("The area of " + s + " is " + s.getArea());

                s = (Shape) new Rectangle(-2, 10);
                System.out.println("The perimeter of " + s +" is " + s.getPerimeter());

                s = (Shape) new Circle(-2);
                System.out.println("The perimeter of " + s +" is " + s.getPerimeter());

                s = (Shape) new Circle(2);
                System.out.println("The area of " + s + " is " + s.getArea());
                }
                catch(Exception e) {
                    System.out.println("Error: " + e.getMessage());
                }
        }
    }

解析.aj

package Shapes;

    privileged public aspect Resolve {
        declare parents: Rectangle implements Shape;
        declare parents: Circle implements Shape;

        public String Rectangle.getName(){
            return "Rectangle";
        }

        public String Circle.getName(){
            return "Circle";
        }

        public String Rectangle.toString(){
            return this.getName()+"("+this.width+","+this.height+")";
        }
        public String Circle.toString(){
            return this.getName()+"("+this.radius+")";
        }

        after() throwing(RuntimeException e) : execution(* Circle.*()){
            handleException();
        }   

        protected void handleException()
        {
            System.out.println("Error detected");
        }
    }

电流输出为：

The area of Rectangle(2.0,10.0) is 20.0

The perimeter of Rectangle(-2.0,10.0) is 16.0

The perimeter of Circle(-2.0) is -12.566370614359172

Error detected

Error: Oops, I don't know how to calculate this :(

我想避免打印“error:oops，我不知道如何计算：（”，我需要得到圆对象的真实面积。但是，我不能更改任何.java文件。所有更改都应使用resolve.aj文件。