java的小问题 extends

public   class   Student{

//字段的定义
private   String   _number;   //学号
private   String   _name;       //姓名
private   int   _age;   //年龄
private   boolean   _sex;   //性别
private   double   _score;     //成绩

public   Student(String   number,String   name,int   age,boolean   sex,double   score){  
//构造方法
this._number   =   number;
this._name   =   name;
this._age   =   age;
this._sex   =   sex;
this._score   =   score;
}

public   void   show(){
//输出
System.out.println( "学号： "   +   _number);
System.out.println( "姓名： "   +   _name);
System.out.println( "年龄： "   +   _age);
System.out.println( "性别： "   +   _sex);
System.out.println( "成绩： "   +   _score);
}

public   static   void   main(String[]   args){
Student   st   =   new   Student( "0001 ", "kog ",25,true,88.7);
st.show();

}
}

现要求定义一个Student的子类 &n