金彦紫砂壶:JAVA的小问题 谢谢大家帮忙 汗啊

public class Student
{
public String sn;
public String name;
public String xueyuan;
public int year;

public Student()
{
sn="02730116";
name="duan";
xueyuan="computer";
year=2002;
}
public void out()
{
System.out.println("学生学号："+sn);
System.out.println("学生姓名："+name);
System.out.println("学生所处学院："+xueyuan);
System.out.println("学生入学年份："+year);
}

public static void main(String arg[])
{
Student st=new Student();
st.out();
}
}

public class xueyuan extends student
{
public int teatherNum;
public int classroomNum;
public int officeNum;

public xueyuan()
{
super();
teatherNum=200;
classNum=58;
officeNum=30;
}
public void out2()
{
System.out.println("教师人数："+teatherNum);
System.out.println("教室数"+classNum);
System.out.println("办公室数"+officeNum);
}

public static void main(String arg[])
{
xueyuan xy=new xueyuan();
xy.out2();
}
}

为什么teather不能继承student呢?
错误代码:

F:\test>javac xueyuan.java
xueyuan.java:1: cannot resolve symbol
symbol : class Student
location: class xueyuan
public class xueyuan extends Student
^
xueyuan.java:11: cannot resolve symbol
symbol : variable classNum
location: class xueyuan
classNum=58;
^
xueyuan.java:17: cannot resolve symbol
symbol : variable classNum
location: class xueyuan
System.out.println("教室数"+classNum);
^
3 errors