What is serialization in Java
💡 Concept: Serialization
Serialization is the process of converting an object into a byte stream for storage or transmission.
📘 Quick Intro
Java serialization enables object persistence and communication by converting objects to a stream of bytes.
🧠 Analogy
Serialization is like packing your belongings into a suitcase so you can transport or store them.
🔧 Technical Explanation
- Java objects must implement the Serializable interface to be serialized.
- Serialization writes the object's state to a byte stream.
- Deserialization reconstructs the object from the byte stream.
- Transient fields are not serialized.
- Used in Java RMI, caching, session replication, and more.
🎯 Use Cases
- ✅ Persist objects to files or databases.
- ✅ Transfer objects over network connections.
- ✅ Enable deep cloning via serialization.
💻 Example: Basic Serialization
import java.io.Serializable;
import java.io.FileOutputStream;
import java.io.ObjectOutputStream;
public class Employee implements Serializable {
private String name;
private int id;
public Employee(String name, int id) {
this.name = name;
this.id = id;
}
// getters and setters
}
public class SerializeDemo {
public static void main(String[] args) throws Exception {
Employee emp = new Employee("John", 123);
FileOutputStream fileOut = new FileOutputStream("employee.ser");
ObjectOutputStream out = new ObjectOutputStream(fileOut);
out.writeObject(emp);
out.close();
fileOut.close();
}
}
❓ Interview Q&A
Q1: What is serialization?
A: Conversion of object to byte stream.
Q2: What interface must be implemented for serialization?
A: Serializable.
Q3: What is transient?
A: Fields not serialized.
Q4: How to deserialize?
A: Use ObjectInputStream.
Q5: Can static fields be serialized?
A: No.
Q6: What is serialVersionUID?
A: Used for version control.
Q7: What exceptions occur in serialization?
A: NotSerializableException.
Q8: Is serialization secure?
A: Has security concerns.
Q9: Can non-serializable objects be serialized?
A: No.
Q10: What are uses of serialization?
A: Persistence and communication.
📝 MCQs
Q1. What is serialization?
- Object to byte stream
- Byte stream to object
- Data encryption
- Compression
Q2. Which interface is needed?
- Serializable
- Externalizable
- Cloneable
- Runnable
Q3. What does transient do?
- Includes fields
- Excludes fields
- Makes fields static
- Deletes fields
Q4. How to deserialize?
- ObjectOutputStream
- ObjectInputStream
- FileOutputStream
- FileInputStream
Q5. Are static fields serialized?
- Yes
- No
- Sometimes
- Depends
Q6. What is serialVersionUID?
- Serialization method
- Version control
- Encryption key
- Thread-safe identifier
Q7. Common exception?
- IOException
- NotSerializableException
- ClassNotFoundException
- NullPointerException
Q8. Is serialization secure?
- Always secure
- Has concerns
- Never secure
- Optional
Q9. Can non-serializable be serialized?
- Yes
- No
- Maybe
- Depends
Q10. Uses of serialization?
- Encryption
- Persistence, communication
- Compression
- Debugging
💡 Bonus Insight
Serialization is fundamental for Java object persistence and distributed systems communication.
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