In java u can access the data through objects.Here Object class is a super/base/parent class for all the java classes,so it will be hold all class objects of java.And also whenever u can serialize the object into the Stream we must store as form of ObjectStream object only and at the time of Deserialize the object from the Streams, u must get it as form of Object class object only.After that u must casting the object to u r Knowing class.
example: here file.txt is a file. And we can write the object into it,and read the object from it.
//write the object into the file,txt,and our class name is MyClass it object is "mco"
FileOutputStream fis=new FileOutputStream("file.txt");
ObjectOutpurStream oss=new ObjectOutputStream(fis);
os.writeObject(mco);
//read the object from the file.txt
FileIutputStream fos=new FileIutputStream(file.txt);
ObjectInputStream ois=new ObjectInputStream(file.txt);
MyClass myObj=(MyClass)ois;//here ois return the Object Class object only that's way we must the casting.