Groovy:动态语言

class Car{
    def run(){
        println "car run"
    }
}

class Bike {
    def run() {
        println "bike run"
    }
}

void func(transport) {
    if(transport.respondsTo('run'))
        transport.run()
}

func(new Car())
func(new Bike())
func('')
输出：
car run
bike run
null
size
class java.lang.Object