Singleton Design Pattern

This is the mostly commonly asked interview question. Answering it correctly along with coding will give you a huge edge. Let’s dive right in.

𝗪𝗵𝗮𝘁 𝗶𝘀 𝘁𝗵𝗲 𝗦𝗶𝗻𝗴𝗹𝗲𝘁𝗼𝗻 𝗣𝗮𝘁𝘁𝗲𝗿𝗻?

Ever needed exactly one instance of a class throughout your entire application? That's where Singleton comes in.

It is one of the patterns from the Creational group, which focuses on instantiating an object or a group of related objects.

𝗪𝗵𝗲𝗻 𝘀𝗵𝗼𝘂𝗹𝗱 𝗜 𝗶𝗺𝗽𝗹𝗲𝗺𝗲𝗻𝘁 𝗶𝘁

Use a Singleton when you need a single point of control, such as a database connection pool, logger, or configuration manager. Multiple instances would waste resources or cause conflicts.

𝗛𝗼𝘄 𝘁𝗼 𝗶𝗺𝗽𝗹𝗲𝗺𝗲𝗻𝘁 𝗶𝘁

The pattern restricts a class to create only one instance. It provides global access to that instance through a static method.

In practice, the class keeps a static reference to itself. When someone asks for an instance, it either creates one (if none exists) or returns the existing one. Thread safety matters here, especially in multi-threaded environments.

Common approaches include eager initialization (creating objects at startup), lazy initialization (creating objects when first needed), or using enums in languages that support them.

𝗪𝗵𝘆 𝗶𝘁 𝘄𝗼𝗿𝗸𝘀