Problem reading from file

Question

Hi,
im bit new to java and i am having this problem. I have a Hashtable of 42000 keys and each value points to an object (vector of arrays). I am storing this hashtable to a file using ObjectOutputStream. the file size is 25 mb. no problem till this point.
I am using ObjectInputStream for reading this object from the file. file is loaded successfully but it takes too much time (1 min to load 25mb file). is there a way to improve the function so it wont take that much time. here is my read function
try{  
FileInputStream f_in = new FileInputStream ("data.dat");
ObjectInputStream obj_in = new ObjectInputStream (f_in);
Object obj = obj_in.readObject (); // here is the problem. obj_in.readObject() takes 1 min to load
if(obj instanceof java.util.Hashtable){
Hashtable idx1 = new Hashtable();
idx1 = (Hashtable) obj;
return idx1;
else{
System.out.println("loading failed!");
catch (Exception e)
System.out.println (e.toString ());
}

Answer 1

it still taking that much time.
the problem is here
Object obj = obj_in.readObject ();
Are you saying you do not gain any time at all using a buffered stream?
In any case, there is no way (I know of) to improve the execution time of deserialization itself. What needs to happen, i.e. reading a lot of bytes from a file + re-constructing a lot of objects, needs to happen. Often disk access will turn out to be a bottleneck; using a buffered stream to the file can improve the speed of this part. But the object reconstruction can not be improved. You could profile your application to find out where exactly the bottleneck is, but I don't see how you can speed it up even if you do know if it's disk access or reconstruction.
If there is a way to speed up the reconstruction process during deserialization, I'd be very interested to know how, actually.
If the runtime is simply unacceptable for your requirements, you might consider looking into using something else then Java serialization to write/read your data.