java题！

Java code:
package f;

public class TestStudent {

public static void main(String[] args) {
Student s1 = new Student();//创建父类对象
Xue x1 = new Xue();//创建子类对象;
s1.Set("张三 ", "男 ");
s1.Set(18);
s1.Set(88.8);
System.out.println(s1.Info());
x1.Set("李四 ","男 ");
x1.Set("厨师");
x1.Set(18);
x1.Set(99.9);
System.out.println(x1.Info());
Student s2 = new Xue();
s2.Set("小王","女");
s2.Set(26);
s2.Set(33.3);
}
}
class Student{ //父类
String name;
String xingbie;
int age;
double chengji;

public void Set(String name,String xingbie){
this.name = name;
this.xingbie = xingbie;
}

public void Set(int age){
this.age = age;
}
public void Set(double chengji){
this.chengji = chengji;
}

public String GetName(){
return name;
}
public String GetXingBie(){
return xingbie;
}
public int GetAge(){
return age;
}
public double GetChengJi(){
return chengji;
}
public String Info(){
return "名字:" + name + "性别:" + xingbie + "年龄:" + " " + age + " " + "成绩:" + chengji;
}
}
class Xue extends Student{ //子类 集成了父类
String zhiwu;
public void Set(String zhiwu){
this.zhiwu = zhiwu;
}
public String GetZhiWu()