Singleton Design Pattern: A Simple Way to Create Singleton Objects

What is Singleton Design Pattern?

The Singleton design pattern is –

• A Creational Design Pattern
• Used for resource-intensive objects
• Restricts multiple instantiations of a class and ensures that only one instance of the class exists in the JVM
• Provides a global access point to get the instance of the class
• Some common uses are logger objects, driver objects, caching, thread pools, database connections, etc.

Typical implementation

• Private constructor
• Private static variable
• Public static method [Global access point]

Challenges and Resolution for Singleton Objects

• Break By Reflection challenge and it’s fix
• Serialization & Deserialization issue and its fix
• Cloning Problem & its solution
• Multithreaded Environment Problem and Solution
• Multiple ClassLoader problem & Fix
• Other Robust ways to create singleton
• Garbage Collection issue and fix

Break by Reflection Problem

Break by Reflection Problem – Fixed

Serialization & Deserialization issue

Serialization & Deserialization issue – Fixed

Cloning Problem in Singleton

Cloning Problem in Singleton – Fixed

Multithreaded environment problem

Multithreaded environment problem – Fix

Multiple Classloader problems & Fix

Other robust ways to create a singleton

Static Holder Pattern

Singleton using Enum

Garbage Collection issue and fix

Here is the GitHub link with the example code – https://github.com/webfuse2017/design-pattern-demo

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