同志们帮我调试一下!谢谢啊!

class Student
{
int useless=0;
void wish()
{
System.out.print("努力学习各种知识!");
}
void speed()
{
System.out.print("我现在唯一的心愿是:");
wish();
}
}
class GraduateStudent extends Student
{
void wish()
{
System.out.print("好好学习,报效祖国!");
}
}
class UndergraduateStuadent extends Stuadent
{
void wish()
{
System.out.print("好好学习,天天向上!");
}
}
class Wishs
{
Student[]person=new Student[4];
void initialize()
{
person[0]=new GraduateStudent();
person[1]=new GraduateStudent();
person[2]=new GraduateStudent();
person[3]=new GraduateStudent();
}
void printWishes()
{
for(int i=0;i person[i].wish();
}
}
class student
{
public void main(String[]args)
{
Wishes youWant=new Wishes();
youWant.initialize();
youWant.printWishes();
}
}