🧠 Java Concepts Deep Dive (Q31–Q40)

31. ❓ Purpose of the `Optional` Class

The Optional<T> class is a container object used to contain not-null objects. It helps avoid NullPointerException.

✅ Benefits:

Represents optional values clearly.
Encourages null-safe code.

32. 🧪 try-with-resources Statement

Introduced in Java 7, this statement ensures that each resource is closed automatically after use.

try (BufferedReader br = new BufferedReader(new FileReader("file.txt"))) {
    // Read file
}

✅ Benefits: No need for finally block to close resources.

Works with classes implementing AutoCloseable.

📌 Try-With-Resources Explained

33. 🔁 final vs finally vs finalize()

Keyword Description final Prevents modification of variables, methods, or classes. finally Ensures execution of code after try-catch. finalize() Called by GC before object is destroyed (deprecated in Java 9+). 📌 Final vs Finally vs Finalize

34. ⚡ volatile Keyword

The volatile keyword ensures that changes to a variable are visible to all threads.

✅ Use Case: Prevents caching of variables in threads.

Ensures memory consistency.

📌 Volatile Keyword Explained

35. 🧱 Design Patterns

Design patterns are reusable solutions to common software design problems.

🧩 Examples: Singleton Factory Observer Builder Strategy

📌 Design Patterns in Java

36. 🧍 Singleton Design Pattern

Ensures a class has only one instance and provides a global access point.

class Singleton {
  private static Singleton instance;
  private Singleton() { }
  public static Singleton getInstance() {
    if (instance == null) {
      instance = new Singleton();
    }
    return instance;
  }
}

📌 Singleton Pattern Guide

37. 🗃️ JDBC (Java Database Connectivity)

JDBC is an API for connecting Java applications to databases.

🔄 Steps: Load JDBC driver. Establish connection. Execute SQL queries. Close connection.

38. 🆚 Statement vs PreparedStatement

Feature Statement PreparedStatement Query Type Static Dynamic Performance Slower Faster (precompiled) SQL Injection Safe ❌ No ✅ Yes 📌 PreparedStatement Guide

39. 🚫 transient Keyword

The transient keyword is used to exclude fields from serialization.

java transient int tempData; 📌 Transient Keyword Explained

40. 🔄 Serialization & Deserialization

Concept Description Serialization Converts an object into a byte stream. Deserialization Reconstructs the object from the byte stream. ✅ Use Case: Saving object state.

Sending objects over a network.