import java.io.*;

class Student implements Serializable{
    private String name;
    public Student(String name){
        this.name=name;
    }
    public String getName(){
        return this.name;
    }
    public String toString(){
        return "姓名："+this.name;
    }
}
public class MyDemo{ 
    public static void main(String[] args) throws IOException, ClassNotFoundException{
        FileOutputStream fos=new FileOutputStream("m.dat");
        ObjectOutputStream oos=new ObjectOutputStream(fos);
        oos.writeObject(new Student("ahah"));
        oos.writeObject(new Student("papa"));
        System.out.println("ok!");
        oos.close();
        fos.close();
    //    
        FileInputStream fis=new FileInputStream("m.dat");
        ObjectInputStream ois=new ObjectInputStream(fis);
        while(ois.readObject()!=null){//这一行错了，是为什么？
            Student stu1=(Student)ois.readObject();
            System.out.println(stu1);
        }
        ois.close();
        fis.close();    
    }
}

ok!
姓名：papa
Exception in thread "main" java.io.EOFException
    at java.io.ObjectInputStream$BlockDataInputStream.peekByte(ObjectInputStream.java:2571)
    at java.io.ObjectInputStream.readObject0(ObjectInputStream.java:1315)
    at java.io.ObjectInputStream.readObject(ObjectInputStream.java:369)
    at MyDemo.main(MyDemo.java:27)

public class MyDemo{ 
    public static void main(String[] args) throws IOException, ClassNotFoundException{
        FileOutputStream fos=new FileOutputStream("m.dat");
        ObjectOutputStream oos=new ObjectOutputStream(fos);
        oos.writeObject(new Student("ahah"));
        oos.writeObject(new Student("papa"));
        System.out.println("ok!");
        oos.close();
        fos.close();
    //    
        FileInputStream fis=new FileInputStream("m.dat");
        ObjectInputStream ois=new ObjectInputStream(fis);
    Student s;                    //定义Student类变量.
        while((fis.available()>0)&&(s=            //判断是否到文件尾。
                (Student)ois.readObject())!=null){
            //Student stu1=(Student)ois.readObject();    //再运行就读了下一个了。
            System.out.println(s);
        }
        ois.close();
        fis.close();    
    }
}