feat: implement serialization and deserialization with static and transient fields

WHAT:
- Added `StudentFinal` class implementing `Serializable`.
- Demonstrated behavior of `static` and `transient` fields during object serialization.
- Implemented `SerilalizationOutputStreamFinal` to serialize a `StudentFinal` object to file.
- Implemented `SerilalizationIutputStreamFinal` to deserialize and print object details.

WHY:
- To illustrate how Java handles object persistence using `ObjectOutputStream` and `ObjectInputStream`.
- To show that:
  - `static` fields are not serialized (they belong to the class, not the instance).
  - `transient` fields are skipped during serialization for security or performance reasons.

KEY POINTS:
- `StudentFinal` contains:
  - `rollno`, `name`, `avg`, `dept` → serialized normally.
  - `Data` (static) → not persisted in file, retains default/class value after deserialization.
  - `t` (transient) → not serialized, resets to default value (`0` for int) upon deserialization.
- Serialization: `SerilalizationOutputStreamFinal` writes object state to `Student3.txt`.
- Deserialization: `SerilalizationIutputStreamFinal` reads object back and prints values.

REAL-WORLD USE CASES:
- Transient fields: used to skip sensitive info like passwords, security tokens, or cache references.
- Static fields: excluded since they represent class-wide state, not per-object data.

NOTES:
- Always close streams after use to avoid resource leaks.
- For consistency across JVM versions, explicitly define `serialVersionUID` in serializable classes.

Signed-off-by: https://github.com/Someshdiwan <[email protected]>

Author: Someshdiwan

Section23JavaIOStreams/Serialisation Storing Data in a File/src/SerilalizationIutputStreamFinal.java

@@ -2,7 +2,7 @@
 
 public class SerilalizationIutputStreamFinal {
     public static void main(String[] args) throws Exception {
-        FileInputStream fis = new FileInputStream("C:\\Users\\somes\\Downloads\\JAVA SE\\Section23JavaIOStreams\\Serialisation Storing Data in a File\\MyJAVA\\Student3.txt");
+        FileInputStream fis = new FileInputStream("/Users/somesh/Java SE/JavaEvolution-Learning-Growing-Mastering/Section23JavaIOStreams/src/MyJAVA/Student3.txt");
         ObjectInputStream ois = new ObjectInputStream(fis);
 
         StudentFinal s = ( StudentFinal ) ois.readObject();
@@ -11,4 +11,50 @@ public static void main(String[] args) throws Exception {
         fis.close();
         ois.close();
     }
-}
+}
+
+/*
+1. Serialization kya hai?
+   - Object → file/stream me binary form me convert karna.
+   - Isse object ko disk pe save ya network ke through transfer kar sakte ho.
+   - Java me `ObjectOutputStream` ka use hota hai.
+
+2. Deserialization kya hai?
+   - File/stream se binary form → original object banata hai.
+   - Java me `ObjectInputStream` ka use hota hai.
+
+3. Important keywords:
+   - `implements Serializable` → bina iske class serialize nahi hogi (NotSerializableException aayega).
+   - `transient` → jis variable pe lagao, wo serialize nahi hoga.
+   - `static` → static variables class-level hote hain, object ke state ka part nahi bante, isliye ye bhi serialize nahi
+      hote.
+
+4. Code Explanation:
+   - `SerilalizationOutputStreamFinal`:
+     - FileOutputStream + ObjectOutputStream banaya.
+     - StudentFinal ka ek object create kiya aur `oos.writeObject(s);` kiya.
+     - File me pura object save ho gaya (binary form me).
+
+   - `SerilalizationIutputStreamFinal`:
+     - FileInputStream + ObjectInputStream banaya.
+     - `readObject()` karke wapas `StudentFinal` type cast kiya.
+     - Print kiya → object state restore ho gayi.
+
+5. Output Behaviour:
+   - `rollno, name, avg, dept` → serialize + deserialize hote hain properly.
+   - `static Data` → serialize nahi hota. Lekin constructor me last value set hoti hai, deserialization ke baad
+      class-level value hi dikhegi (500).
+   - `transient t` → serialize nahi hota, isliye deserialization ke baad iska value default ho jaata hai (0).
+
+6. Best Practices:
+- Always use `serialVersionUID` in Serializable classes → version control ke liye.
+- Streams ko close karne ke liye try-with-resources use karo.
+- Agar sensitive data hai (password etc.), usko `transient` mark karo.
+
+
+✔ `Serializable` → required
+✔ `transient` → skip during serialization
+✔ `static` → not serialized (class-level)
+✔ `ObjectOutputStream.writeObject()` → save object
+✔ `ObjectInputStream.readObject()` → restore object
+*/

Section23JavaIOStreams/Serialisation Storing Data in a File/src/SerilalizationOutputStreamFinal.java

@@ -34,12 +34,12 @@ public String toString() {
 
 public class SerilalizationOutputStreamFinal {
     public static void main(String[] args) throws Exception {
-        FileOutputStream fos = new FileOutputStream("C:\\Users\\somes\\Downloads\\JAVA SE\\Section23JavaIOStreams\\Serialisation Storing Data in a File\\MyJAVA\\Student3.txt");
+        FileOutputStream fos = new FileOutputStream("/Users/somesh/Java SE/JavaEvolution-Learning-Growing-Mastering/Section23JavaIOStreams/src/MyJAVA/Student3.txt");
         ObjectOutputStream oos = new ObjectOutputStream(fos);
 
         StudentFinal s = new StudentFinal(10, "John", 89.9f, "CSE");
         oos.writeObject(s);
         fos.close();
         oos.close();
     }
-}
+}