如何在groovy lambda表达式中创建抽象类引用

abstract class Animal {
    abstract void makeSound()
}

def animalRef = { Animal animal -> animal.makeSound() }

class Dog extends Animal {
    void makeSound() {
        println "Woof!"
    }
}

class Cat extends Animal {
    void makeSound() {
        println "Meow!"
    }
}

def dog = new Dog()
def cat = new Cat()

animalRef(dog) // 输出：Woof!
animalRef(cat) // 输出：Meow!