一个空指针错误,请大家帮忙看看

各位高手:我用java写一个学生分数管理系统,就实现信息输入,求和,求平均分,排序的功能.全部代码如下,另外还有一个javabean.
package studentmanager;import java.io.*;public class StuSystem {
    BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
    StuBean stbean[] = new StuBean[3];
    //输入信息
    public void InputInfor() {
        System.out.println("----------------请输入学生的成绩信息:------------");
        try {
            for (int i = 0; i < 3; i++) {
                StuBean stu = new StuBean();
                System.out.print("学号:");
                stu.setCode(br.readLine());
                System.out.print("姓名:");
                stu.setName(br.readLine());
                System.out.print("C语言:");
                stu.setAverage(Float.parseFloat(br.readLine()));
                System.out.print("Java:");
                stu.setSum(Float.parseFloat(br.readLine()));                stbean[i] = stu;
               System.out.println("xuehao："+stbean[i].getCourse1());//为什么输出是空的呢
               System.out.println("xuehao："+stbean[i].getCourse2());());//为什么输出是空的呢
            }
        } catch (Exception ex) {
        }
    }
    //求和
    public void SetSum1() {
       for (int i = 0; i < stbean.length; i++) {
           stbean[i].setSum(stbean[i].getCourse1()+stbean[i].getCourse2());
           System.out.println(stbean[i].getName()+"的总分是:"+stbean[i].getSum());
       }
    }
    //求平均分
    public void Sort() {
        for (int i = 0; i < stbean.length; i++) {
            stbean[i].setAverage(stbean[i].getSum()/2);
            System.out.println(stbean[i].getName()+"的平均分是:"+stbean[i].getAverage());
        }
    }
    //按总分排序
    public void SetAvaerage() {
        float flag=0.0f;
        //冒泡排序
        for (int i = 0; i < stbean.length; i++) {
            for (int j = i+1; j <stbean .length; j++) {
                if(stbean[i].getSum()<stbean[j].getSum()){
                    flag = stbean[j].getSum();
                    stbean[j].getSum() = stbean[i].getSum();
                    stbean[i].getSum() = flag;
                }
            }
        }
    }    public static void main(String[] args) {
        StuSystem ss = new StuSystem();
        ss.InputInfor();
        ss.SetSum1();
    }
}为什么stbean[i].getCourse1()是空的??哪位给我解释一下,谢谢!!