Object creation control. When making an object is expensive, or the exact type isn’t known until runtime, or you need exactly one instance, exactly one family of related instances, or a fast supply of near-identical copies, one of these six covers it.

• Singleton Guarantees exactly one instance exists, and makes the lazy double-checked construction safe when multiple threads race to create it first.
• Factory Method One method owns “which concrete class to build,” so every caller picks a type without duplicating the same if/else ladder.
• Abstract Factory Guarantees every object built through one factory belongs to the same family, so you can’t accidentally mix a Windows audio player with a VLC video player.
• Builder Splits required fields, enforced in the constructor, from optional ones set via chained calls, so you skip telescoping constructors and half-built objects.
• Prototype Clones existing instances instead of rebuilding from scratch, using copy constructors instead of Java’s Cloneable.
• Object Pool Reuses a fixed set of expensive objects instead of constructing and discarding a fresh one per request.

← Back to Design Patterns