Singleton Design Pattern Explained
The Singleton pattern ensures a class has only one instance throughout an application's lifetime, and provides a single global point of access to it.
Published October 6, 2026
The Singleton pattern ensures a class has only one instance throughout an application's lifetime, and provides a single global point of access to it.
Why it exists
- Some resources — like a single database connection pool or a shared application configuration — genuinely should exist only once
- Without enforcing this, code might accidentally create multiple instances, leading to inconsistent state or wasted resources
How to apply it
- Implement it by making the constructor private/inaccessible and exposing a static method that returns the one shared instance, creating it on first use
- Use singletons sparingly — they introduce global state, which can make code harder to test and reason about
FAQ
Is Singleton considered an anti-pattern today?
Many developers consider it overused — the global state it introduces can make unit testing harder, and dependency injection often achieves the same goal more flexibly and testably.