类名作为形参和返回值

类名作为形参

其实要的是该类的对象

public class Cat {
    public void eat(){
        System.out.println("cat eat fish");
    }
}

/*
  测试类
 */
public class CatDemo {
    public static void main(String[] args) {
    CatOperator co = new CatOperator();
    Cat c = new Cat();
    co.useCat(c);
    }
}

public class CatOperator {
    public void useCat(Cat c){ //Cat c = new Cat();
        c.eat();
    }
}

类名作为返回值

类名作为形参和类名作为返回值

public class Cat {
    public void eat(){
        System.out.println("cat eat fish");
    }
}

/*
  测试类
 */
public class CatDemo {
    public static void main(String[] args) {
    CatOperator co = new CatOperator();
    Cat c = new Cat();
    co.useCat(c);
        Cat c2 = co.getCat();  //new Cat()
        c2.eat();
    }
}

public class CatOperator {
    public void useCat(Cat c){ //Cat c = new Cat();
        c.eat();
    }
    public Cat getCat(){
        Cat c = new Cat();
        return (c);
    }
}

抽象类名作为形参和返回值

public abstract class Animal {
    public abstract void eat();
}

public class AnimalDemo {
    public static void main(String[] args){
        AnimalOperator ao = new AnimalOperator();
        Animal a= new Cat();
        ao.useAnimal(a);
        Animal a2 = ao.getAnimal();  //new Cat();
        a2.eat();
    }
}

public class Cat extends Animal{
    public void eat(){
        System.out.println("猫吃鱼");
    }
}

public class AnimalOperator {
    public void useAnimal(Animal a){  //Animal a= new Cat();
        a.eat();
    }
    public Animal getAnimal() {
        Animal a = new Cat();
        return a;
    }
}

接口名作为形参和返回值