Try to recover a serialized file without the class of object that's stored in that file : ObjectOutputStream « File « Java Tutorial

1. Java Tutorial
2. File
3. ObjectOutputStream

import java.io.File;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.ObjectInputStream;
import java.io.ObjectOutput;
import java.io.ObjectOutputStream;
import java.io.Serializable;

public class MainClass {
  public static void main(String[] args) throws Exception {
    ObjectOutput out = new ObjectOutputStream(new FileOutputStream("X.file"));
    MyClass zorcon = new MyClass();
    out.writeObject(zorcon);
    
    ObjectInputStream in = new ObjectInputStream(new FileInputStream(new File("X.file")));
      Object mystery = in.readObject();
      System.out.println(mystery.getClass());
    
  }
}

// A serializable class.
class MyClass implements Serializable {
}