Top 75 Java Interview Questions - What are different ways to create singleton class ? #java #coding

Description:

💡 Java Tricky Interview Question 17
Do you know the different ways to create a Singleton class in Java? 🤔 Singleton is one of the most popular and commonly asked design patterns in Java interviews — but there’s more than one way to implement it! In this video, we’ll cover multiple approaches and discuss the pros and cons of each.

🔥 What You’ll Learn in This Video:
✅ What is a Singleton class and why it’s useful
✅ 5 different ways to implement Singleton in Java
✅ Pros, cons, and threadsafety concerns for each approach
✅ When and why to choose one method over another
✅ Best practices for Singleton design

📌 5 Ways to Create a Singleton Class in Java:

1️⃣ Eager Initialization
Creates the instance when the class is loaded.
Simple, threadsafe, but might waste memory if not used.

2️⃣ Lazy Initialization
Creates the instance when it’s first requested.
Not threadsafe by default (can be made threadsafe with synchronization).

3️⃣ Threadsafe Singleton (Synchronized Method)
Uses synchronized access to ensure thread safety.
Simple but may reduce performance due to method synchronization.

4️⃣ DoubleChecked Locking
Combines lazy initialization with efficient threadsafety.
Uses `volatile` and synchronized block only on first access.
Highly recommended in multithreaded environments.

5️⃣ Bill Pugh Singleton (Inner Static Helper Class)
Uses a static inner class to hold the Singleton instance.
Threadsafe, lazyloaded, and doesn’t require synchronization.
Clean, efficient, and widely considered the best practice.

📌 Bonus: Enum Singleton
Implement Singleton using `enum`.
Threadsafe, serializationproof, and prevents reflection attacks.
Cleanest and safest Singleton implementation.

⚠️ Important Notes:
⚠️ Lazyloaded Singletons need careful synchronization in multithreaded apps.
⚠️ Avoid using DoubleChecked Locking without `volatile` in Java 5 and above.
⚠️ Enumbased Singleton is recommended for most use cases due to simplicity and safety.

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