Singleton Design Pattern Readme file

Author: DhirajGadekar

Creational Design Pattern/SingletonDesignPattern/README.md

@@ -1,18 +1,96 @@
-## Getting Started
+# Singleton Design Pattern
 
-Welcome to the VS Code Java world. Here is a guideline to help you get started to write Java code in Visual Studio Code.
+## Overview
 
-## Folder Structure
+The Singleton design pattern ensures that a class has only one instance and provides a global point of access to that instance. It's commonly used when exactly one object is needed to coordinate actions across the system, such as managing a shared resource or controlling access to a limited resource.
 
-The workspace contains two folders by default, where:
+![singleton-1](https://github.com/DhirajGadekar/Design-Patterns/assets/111908836/a6233812-7547-4954-821f-03d6a22764d4)
 
-- `src`: the folder to maintain sources
-- `lib`: the folder to maintain dependencies
+### Key Points
 
-Meanwhile, the compiled output files will be generated in the `bin` folder by default.
+- **Single Instance**: Singleton classes have only one instance that is globally accessible throughout the application.
+- **Global Access**: Provides a global access point to the single instance, allowing it to be easily accessed by other parts of the code.
+- **Lazy Initialization**: Singleton instances can be created either eagerly (at the start) or lazily (when requested), depending on the implementation.
+- **Thread Safety**: Various approaches exist to ensure thread safety during the creation of Singleton instances in multi-threaded environments.
 
-> If you want to customize the folder structure, open `.vscode/settings.json` and update the related settings there.
+## How It Works
 
-## Dependency Management
+### Eager Implementation
 
-The `JAVA PROJECTS` view allows you to manage your dependencies. More details can be found [here](https://github.com/microsoft/vscode-java-dependency#manage-dependencies).
+```java
+public class Singleton {
+    private static final Singleton instance = new Singleton();
+
+    private Singleton() {}
+
+    public static Singleton getInstance() {
+        
+        return instance;
+    }
+}
+```
+### Lazy Implementation
+
+```java
+public class Singleton {
+    private static final Singleton instance;
+
+    private Singleton() {}
+
+    public static Singleton getInstance() {
+        if(instance == null) {
+            instance = new Singleton();
+        }
+        return instance;
+    }
+}
+```
+
+### Thread-Safe Implementation (Double-Checked Locking)
+
+```java
+public class Singleton {
+    private volatile static Singleton instance;
+
+    private Singleton() {}
+
+    public static Singleton getInstance() {
+        if (instance == null) {
+            synchronized (Singleton.class) {
+                if (instance == null) {
+                    instance = new Singleton();
+                }
+            }
+        }
+        return instance;
+    }
+}
+```
+
+### Use Cases
+- **Resource Managers:** Database connection pools, file managers, etc., where a single instance ensures efficient resource utilization.
+- **Configuration Settings:** Holding configuration settings that need to be accessed throughout the application.
+
+### Best Practices
+- **Lazy Initialization:** Use lazy initialization for better resource management unless eager initialization is specifically required.
+- **Thread Safety:** Ensure thread safety in multi-threaded environments when implementing Singleton.
+- **Consider Alternatives:** Consider alternatives like dependency injection frameworks for managing single instances.
+
+### Breaking the Singleton Pattern
+The Singleton pattern can be broken if not implemented correctly:
+1. **Reflection:** Using reflection, it's possible to access the private constructor of a Singleton class and create another instance.
+2. **Serialization and Deserialization:** During deserialization, if not handled properly, it might create a new instance, violating the Singleton pattern.
+3. **Synchronization Issues:** Improper synchronization in a multi-threaded environment can lead to multiple instances being created due to race conditions.
+
+## Contributor :  
+
+<table>
+  <tr>
+    <td align="center"><a href="https://github.com/DhirajGadekar"><img src="https://avatars.githubusercontent.com/u/111908836?v=4" width="100px;" alt="Dhiraj Gadekar"/><br/><sub><b>Dhiraj Gadekar</b></sub></a><br/>
+</tr>
+</table>
+Contributions are welcome! If you have any suggestions, improvements, or additional examples related to the Singleton pattern, feel free to open an issue or submit a pull request.
+
+## Feedback
+
+If you have any feedback, please reach out to us at **<a href="https://mail.google.com/mail/u/3/#inbox?compose=CllgCJTHWNbjZQFnRQlzTNlRVSXcTdxfZVrbtCvTZWPTxTWwgDHTpnckBglPXzNWwkPgMBkrZSq" target="_blank">Email</a>**