java :instanceof用法

package JavaKEYWORDS;

class Bird{//父类

}
class BigBird extends Bird{//Bird的子类

}
class LittleBird extends Bird implements BirdFly{//Bird的子类加上BirdFly接口

}
interface BirdFly{

}
public class JavaKWinstanceof {
    public static void main(String[] args) {
        // TODO Auto-generated method stub
        JavaKWinstanceof myThis=new JavaKWinstanceof();
        Bird myBird=new Bird();
        BigBird myBigBird=new BigBird();
        LittleBird myLittleBird=new LittleBird();
        //打印各实例与类之间的关系
        prt(myThis instanceof JavaKWinstanceof);//打印结果：YES   
        prt(myBird instanceof Bird);//打印结果：YES  
        prt(myBigBird instanceof Bird);//打印结果：YES     子类实例出的对象也是父类的实例
        prt(myBird instanceof BigBird);//打印结果：NO      父类实例出的对象不是子类的实例
        prt(myLittleBird instanceof Bird);//打印结果：YES  子类加上其它接口后实例出的对象也是父类的实例
        /*
         * prt(myLittleBird instanceof BigBird);//编译报错  两个没有继承关系的类之间没有instanceof关系      
         * prt(1 instanceof int);//编译错误           
         */
    }
    //判断及显示A是否为B的实例
    static void prt(boolean A_is_instanceof_B){
       if(A_is_instanceof_B){
           System.out.println("YES");
       }
       else{
           System.out.println("NO");
       }
    }

}