testpolymorphism.java

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public class TestPolymorphism{
	public static void main(String[] args){
		Animal a=new Cat();
		//a.eat();
		//a.sleep();
		//a.call(); error!
		
		/*
			判断a引用指向的对象是否为Dog对象
		*/
		if (a instanceof Dog){
			/*
				把a引用指向的对象强制转换为Dog类型
				强制当作Dog对象看待	
			*/
			Dog d=(Dog)a;
			d.call();
		}
		
		/*
		System.out.println(a instanceof Cat);
		System.out.println(a instanceof Dog);
		System.out.println(a instanceof Animal);
		*/
	}
}
class Animal{
	public void eat(){
		System.out.println("Animal eat");
	}
	public void sleep(){
		System.out.println("sleep 8 hours");	
	}
}
class Dog extends Animal{
	public void call(){
		System.out.println("Dog call");
	}
	public void sleep(){
		System.out.println("sleep 6 hours");
	}
}
class Cat extends Animal{
}