/*编写一个java应用程序，程序中有四个类：People，ChinaPeople，AmericanPeople，BeijingPeople，people类有访问权限是protected的double类型的weight和height以及public void speakHello();public void averageHeight(),public void averageWeight()方法。Chinapeople类是people的子类，新增public void gongfu()方法，以及重写public void speakHello();public void averageHeight(),public void averageWeight()方法。Americanpeople类是people的子类，新增 public void americanBoxing(),以及重写public void speakHello();public void averageHeight(),public void averageWeight()方法。BeijingPeople类是Chinapeople的子类，新增 public void Opera(),以及重写public void speakHello();public void averageHeight(),public void gongfu()方法,public void averageWeight()方法。*/     class People{         protected double height;         protected double weight;         public void speakHello(){             System.out.println("hello");         }         public void averageHeight(){}         public void averageWeight(){}     }     class AmericanPeople extends People{         public void speakHello(){             System.out.println("american i");         }         public void averageHeight(){}         public void averageWeight(){}         public void americanBoxing(){}     }     class ChinaPeople extends People{         public void speakHello(){             System.out.println("china hi");         }         public void averageHeight(){}         public void averageWeight(){}         public void chinaGongfu(){}              }     class BeijingPeople extends ChinaPeople{         public void speakHello(){             System.out.println("BEIJING HI");         }         public void averageHeight(){}         public void averageWeight(){}         public void chinaGongfu(){}         public void beijingOpera(){}              }     public class Alei {         public static void main(String []args){            //创建 子类AmericanPeople的一个实例对象，使用默认构造法             AmericanPeople a=new AmericanPeople();             //方法重写             a.speakHello();             a.averageHeight();             a.averageWeight();            //创建子类ChinaPeople的一个实例对象，使用默认构造法             ChinaPeople b=new ChinaPeople();             //方法重写             b.speakHello();             b.averageHeight();             b.averageWeight();             //创建子类BeijingPeople的实例对象，使用默认构造法             BeijingPeople c=new BeijingPeople();             //方法重写             c.speakHello();             c.averageHeight();             c.averageWeight();             c.chinaGongfu();}}

运行结果如下：

american ichina hiBEIJING HI