如何判断ObjectOutputStream已经结束？
import   java.io.FileInputStream;
import   java.io.FileNotFoundException;
import   java.io.FileOutputStream;
import   java.io.IOException;
import   java.io.ObjectInputStream;
import   java.io.ObjectOutputStream;
import   java.io.Serializable;

public   class   ObjectOutputStreamu   {

public   static   void   main(String[]   args)   {

try   {
FileOutputStream   fos   =   new   FileOutputStream( "a.txt ");
ObjectOutputStream   oos   =   new   ObjectOutputStream(fos);
Employee   e1   =   new   Employee(30,   "jack ",   100);
Employee   e2   =   new   Employee(30,   "jack ",   99.999999);
Employee   e3   =   new   Employee(30,   "jack ",   99.999998);
oos.writeObject(e1);
oos.writeObject(e2);
oos.writeObject(e3);
oos.close();    
FileInputStream   fis   =   new   FileInputStream( "a.txt ");
ObjectInputStream   ois   =   new   ObjectInputStream(fis);
Object   o;
while((o   =   ois.readObject())   !=   null)   {     //   这个判断怎么没有起到作用？最后还是跳出异常 if   (o   instanceof   Employee)
System.out.println(((Employee)o).name   +   ": "   +   ((Employee)o).age   +   ": "   +   ((Employee)o).score);     }

}   catch   (FileNotFoundException   e)   {
//   TODO   Auto-generated   catch   block
e.printStackTrace();
}   catch   (IOException   e)   {
//   TODO   Auto-generated   catch   block
e.printStackTrace();
}   catch   (ClassNotFoundException   e)   {
//   TODO   Auto-generated   catch   block
e.printStackTrace();
}
}

}


class   Employee   implements   Serializable
{
int   age;
String   name;
double   score;

public   Employee(int   age,   String   name,   double   score)
{
this.age   =   age;
this.name   =   name;
this.score   =   score;
}

public   Employee()   {
}
}

------解决方案--------------------
判断流到头 的结果返回的是-1不是null


------解决方案--------------------
while(ois.available()> 0)