java-多态2

多态的意义：

不按照多态的代码：

package day10;

public class TestPloy2 {
	public static void main(String[] args) {
		Dog1 a0 = new Dog1();
		Cat1 a1 = new Cat1();
		Monkey1 a2 = new Monkey1();
		Tiger a3 = new Tiger();
		Sheep a4 = new Sheep();
		Cock a5 = new Cock();
		a0.eat();
		a1.eat();
		a2.eat();
		a3.eat();
		a4.eat();
		a5.eat();
	}
}

class Animal1 {
	public void eat() {

	}
}

class Dog1 extends Animal1 {
	public void eat() {
		System.out.println("Dog eats bone");
	}
}

class Cat1 extends Animal1 {
	public void eat() {
		System.out.println("Cat eats fish");
	}
}

class Monkey1 extends Animal1 {
	public void eat() {
		System.out.println("Monkey eats banana");
	}
}

class Tiger extends Animal1 {
	public void eat() {
		System.out.println("Tiger eats hunam");
	}
}

class Sheep extends Animal1 {
	public void eat() {
		System.out.println("Sheep eats grass");
	}
}

class Cock extends Animal1 {
	public void eat() {
		System.out.println("Cock eats rice");
	}
}

　运行截图：

按照多态的思路：

 

package day10;

public class TestPloy2 {
	public static void main(String[] args) {
		/*
		 * Dog1 a0 = new Dog1(); Cat1 a1 = new Cat1(); Monkey1 a2 = new Monkey1(); Tiger
		 * a3 = new Tiger(); Sheep a4 = new Sheep(); Cock a5 = new Cock(); a0.eat();
		 * a1.eat(); a2.eat(); a3.eat(); a4.eat(); a5.eat();
		 */
//		Animal1[] as=new Animal1[] {new Dog1(),new Cat1(),new Tiger(),new Monkey1(),new Sheep(),new Cock()};
		Animal1[] as = { new Dog1(), new Cat1(), new Tiger(), new Monkey1(), new Sheep(), new Cock() };
		for (int i = 0; i < as.length; i++) {
				as[i].eat();
		}
	}

}

class Animal1 {
	public void eat() {

	}
}

class Dog1 extends Animal1 {
	public void eat() {
		System.out.println("Dog eats bone");
	}
}

class Cat1 extends Animal1 {
	public void eat() {
		System.out.println("Cat eats fish");
	}
}

class Monkey1 extends Animal1 {
	public void eat() {
		System.out.println("Monkey eats banana");
	}
}

class Tiger extends Animal1 {
	public void eat() {
		System.out.println("Tiger eats hunam");
	}
}

class Sheep extends Animal1 {
	public void eat() {
		System.out.println("Sheep eats grass");
	}
}

class Cock extends Animal1 {
	public void eat() {
		System.out.println("Cock eats rice");
	}
}

　　运行结果：

　　　　　　　　　　　　　　　　　　　　

　　可以看到，运行结果和之前是一样的。但是代码比之前简洁了。

　　小结：多态的作用就在于把不同子类的对象，统一看做是父类对象来处理，屏蔽了不同子类的差异，使得代码具有更好的通用性。

buy动物例子-多态：

代码：

package day10;

public class TestPloy2 {
	public static void main(String[] args) {
		/*
		 * Dog1 a0 = new Dog1(); Cat1 a1 = new Cat1(); Monkey1 a2 = new Monkey1(); Tiger
		 * a3 = new Tiger(); Sheep a4 = new Sheep(); Cock a5 = new Cock(); a0.eat();
		 * a1.eat(); a2.eat(); a3.eat(); a4.eat(); a5.eat();
		 */
//		Animal1[] as=new Animal1[] {new Dog1(),new Cat1(),new Tiger(),new Monkey1(),new Sheep(),new Cock()};
//		Animal1[] as = { new Dog1(), new Cat1(), new Tiger(), new Monkey1(), new Sheep(), new Cock() };
		/*
		 * for (int i = 0; i < as.length; i++) { as[i].eat(); }
//		 */
//		feed(new Dog1());
//		feed(new Cat1());
//		feed(new Monkey1());
		Animal1 a=buyAnimal(2);
		System.out.println(a);//返回对象
		Animal1 b=buyAnimal(3000);
		System.out.println(b);
	}

	/*
	 * static void feed(Dog1 d) {
	 * 
	 * } static void feed(Cat1 c) {
	 * 
	 * } ...
	 */
	static void feed(Animal1 a) {
		a.eat();//传什么动物，就调用什么方法
	}
	static Animal1 buyAnimal(int money) {
		if(money<5) return new Cock();
		else if(money<50) return new Cat1();
		else if(money<200) return new Dog1();
		else if(money<500) return new Sheep();
		else if(money<2000) return new Monkey1();
		else return new Tiger();
	}
}

class Animal1 {
	public void eat() {

	}
}

class Dog1 extends Animal1 {
	public void eat() {
		System.out.println("Dog eats bone");
	}
}

class Cat1 extends Animal1 {
	public void eat() {
		System.out.println("Cat eats fish");
	}
}

class Monkey1 extends Animal1 {
	public void eat() {
		System.out.println("Monkey eats banana");
	}
}

class Tiger extends Animal1 {
	public void eat() {
		System.out.println("Tiger eats hunam");
	}
}

class Sheep extends Animal1 {
	public void eat() {
		System.out.println("Sheep eats grass");
	}
}

class Cock extends Animal1 {
	public void eat() {
		System.out.println("Cock eats rice");
	}
}

　　运行截图：

 

 　　多态用在参数上 m(A,a)：m方法允许A类或A的某个子类对象作为实参。

　　多态作用在返回值上 A m():m方法返回的是A类或A的某个子类对象。