Groovy动态类型

class Rectangle {    void draw() {        PRintln "Rectangel draw"    }}class Circle {    void draw() {        println "Circle draw"    }    def getRadius() {        return 10    }}class Oval {    void draw() {        println "Oval draw"    }}void draw(shape) {    shape.draw()        if (shape.metaClass.respondsTo(shape, "getRadius")) {        println "radius = ${shape.getRadius()}"    }}draw(new Rectangle())draw(new Circle())draw(new Oval())// 返回Rectangel drawCircle drawradius = 10Oval draw