Can't resolve java.io.EOFException?

Question

This is my first file

   public class ObjectStream 
     {
       public static void main(String args[]) throws FileNotFoundException, IOException
     {
     java.io.File f=new java.io.File("D:Employee.outt") ;  
      Employee e=new Employee("John");
      Employee e1=new Employee("Mary");
         Employee e2=new Employee("Christian");
       OutputStream os=new java.io.FileOutputStream(f);

       java.io.ObjectOutputStream oos=  new ObjectOutputStream(os);
      oos.writeObject(e);
       oos.writeObject(e1);
         oos.writeObject(e2);
      }
      }

This is my second file

    public class Employee implements java.io.Serializable
    {
     private static int count=100;
    private int eid;
     private String ename;

     public Employee()
    {
     count++;
     this.eid=count;        
    }

    public Employee(String ename)
   {
    this();
    this.ename=ename;        
    }

    public static int getCount() {
       return count;
     }

    public static void setCount(int count) {
      Employee.count = count;
     }

     public int getEid() {
      return eid;
      }

    public void setEid(int eid) {
      this.eid = eid;
    }

    public String getEname() {
      return ename;
     }

     public void setEname(String ename) {
         this.ename = ename;
   }

   }

This is my third file

      public class MainClass
    {
         public static void main(String args[]) throws FileNotFoundException,        IOException, ClassNotFoundException
       {
        File f=new File("D:Employee.outt");
       byte data[]=new byte[(int)f.length()];
    InputStream is=new java.io.FileInputStream(f);
      java.io.ObjectInputStream ois=new java.io.ObjectInputStream(is);
    Object o=ois.readObject();



    while(o!=null)
         {
   Employee e=(Employee)o;
   System.out.println(e.getEid());
   System.out.println(e.getEname());
     o=ois.readObject();
       }


    ois.close();
    is.close();
     }
     }

I am trying to read objects stored in Employee.outt in via this third file but it is reading all the objects but at the end throwing

Exception in thread "main" java.io.EOFException.

I don't know how to resolve it.

Answer 1

while(o!=null)

This isn't a valid way to read an ObjectInputStream. The readObject() method only returns a null if you wrote a null. At end of stream it throws, guess what, an EOFException, so the correct way to read the stream is to loop calling `readObject() until you catch that exception, then break and close the stream.

at the end of file it is giving EOF exception

That's exactly what EOFException means.

Answer 2

You should close ObjectOutputStreamin ObjectStream class.

oos.writeObject(e);
oos.writeObject(e1);
oos.writeObject(e2);

oos.close();

In the MainClass you can use a try-finally block to close the inputstream.

try
{   
  InputStream is=new java.io.FileInputStream(f);
  java.io.ObjectInputStream ois=new java.io.ObjectInputStream(is);    

    // READ logic here   
}
finally
{    
 ois.close();
 is.close();  
}

Answer 3

1. You really should flush and close the object output stream in "first file".

2. You only need to close 'ois' in "third file". The other stream is automatically closed for you.

3. If you know how many objects you're going to write, change "first file" to write the number of objects following first, then change "third file" to read that number and only read that many objects. That way, you never get the EOF exception, because you stop reading when you've read the last object.

As EJP pointed out, you still have to catch the EOFException, because the file you're reading might be damaged.

In First File:

...
oos.writeInt(3);
oos.writeObject(e);
...

In Third File:

...
try {
  int numObjects = ois.readInt();
  for( int a = 0; a < numObjects; ++a ) {
      ...
  }
} catch( EOFException e ) {
    ...
}