Serialization

[Allen Bandela]

Hi there!
I wonder what exactly happens to a static variable that has been declared and initialized in a class that implements Serializable and when that class is passed to an output stream with the writeObject() method as follows:

 
package serializers;
import java.io.*;
public class TestSer {
public static void main(String[] args){
SpecialSerial s=new SpecialSerial();
try{
ObjectOutputStream os=new ObjectOutputStream(new FileOutputStream("myFile"));
os.writeObject(s); os.close();
System.out.println(++s.z + " ");

ObjectInputStream is=new ObjectInputStream(new FileInputStream("myFile"));
SpecialSerial s2=(SpecialSerial)is.readObject();
is.close();
System.out.printl(s2.y + " " + s2.z);
}catch(Exception x){System.out.println("exc");}
}
}
 
class SpecialSerial implements Serializable{
transient int y=7;
static int z=9;
}
 
   

Output: 10 0 10

As static variables would not be serialized, should'nt s2.z return 0? What exactly is happening here. Can someone explain?

[wise owen]

    
class SpecialSerial implements Serializable {
  transient int y=7;
  static int z=9;
}
 
public class A {
  public static void main(String[] args){
    SpecialSerial s=new SpecialSerial();
    try{
      ObjectOutputStream os=new ObjectOutputStream(new FileOutputStream("myFile"));
      os.writeObject(s); 
      os.close();
      System.out.println(++s.z + " ");     
 
    }
    catch(Exception x){
      System.out.println("exc");

    }
  }
} 
 
public class B {
  public static void main(String[] args){
    SpecialSerial s=new SpecialSerial();
    try{
     
      ObjectInputStream is=new ObjectInputStream(new FileInputStream("myFile"));
      SpecialSerial s2=(SpecialSerial)is.readObject();
      is.close();
      System.out.println(s2.y + " " + s2.z);
 
    }
    catch(Exception x){
      System.out.println("exc");

    }
  }
} 

Run B.class after runing A.class. You will get s2.z=9. because z is static member and will initialized when the class is loaded (first time).

[James Quinton]

don't get confused by transient.
after being deserialized, transient variable is reset to its default value, while static variable keeps its original value