Block application until the modification of a File

Question

Hi, I have an application that saves and reads a Hashtable from disk. The code is the next one and it runs fine. However I want to allow two applications reading and saving in the same file (both in java). I want both applications to share the same data. My idea was that before to save the hastable the application reads the hastable from the file and make a new hastable with the information of both. Then the application should save the new hashtable (i know that for a while both application are not sincronized...but it is not important ). The problem is when one application wants to save its hashtable (that has been modified) while the other application is doing the same. I'd like that one application could detect that other application is working the in the file and block itself until the other finishes.
Any idea?
Thanks in advance
Marc
Curent code:
private Hashtable load(File fileDisk)throws Exception{
BufferedInputStream is;
Hashtable hs;
if (fileDisk.length()!=0){
// the file is not empty
is = new BufferedInputStream(new FileInputStream(fileDisk));
ObjectInputStream ois = new ObjectInputStream(is);
hs = (Hashtable) ois.readObject();
ois.close();
else{
hs = new Hashtable();
return hs;

Answer 1

Use Serialization and save yourself a fortune of time.
RE: java.io.Serializable.