多态

package java_test;


import org.junit.Test;


/**
 * Polymorphic  多态
 * @author Administrator
 *
 */
class  Poly1{
void speak(){
System.out.print("speak1"+" ");
}
void sleep(){
System.out.print("sleep1"+" ");
}


}




class Poly2 extends Poly1 {
void speak(){
System.out.print("speak2"+" ");
}
void skip(){
System.out.print("skip"+" ");
}


}




class Polymorphic{
@Test
public static void main(String[] args){
Poly1 poly1 = new Poly2();
poly1.speak();
poly1.sleep();
//poly1.skip();  报错

Poly2 poly2 = (Poly2)poly1;
poly2.skip();
poly2.sleep();
poly2.speak();

}

}

输出：speak2 sleep1 skip sleep1 speak2 

总结：

@1，继承

@2，覆盖

@3，父类引用指向子类对象