java/w5/Shape.java

package w5;

public abstract class Shape {
    public abstract void draw();
}
    class Circle extends Shape {
        @Override
        public void draw() {
            System.out.println("绘制一个圆形");
        }
    }
    class Rectangle extends Shape {
        @Override
        public void draw() {
            System.out.println("绘制一个矩形");
        }
    }
class ShapeTest {
        public static void drawShape(Shape s) {
            s.draw();
        }
        public static void main(String[] args) {
            Shape circle = new Circle();
            Shape rectangle = new Rectangle();
            drawShape(circle);
            drawShape(rectangle);
        }
    }