创建型模式

A class has one and only one instance, with Java and Go implementations including eager, lazy, DCL, static-inner-class, enum, mutex, and sync.Once approaches.

The factory-method pattern uses multiple factory classes and delays concrete product creation to subclasses.

The builder pattern constructs a complex object from many smaller parts; the builder creates the parts and the director assembles them.

Prototype-pattern notes with UML, Java and Go clone examples, plus a generic DAO example that returns cloned data.

Abstract-factory notes showing related product families and a Go implementation with engines, wheels, factories, and a client.

Simple-factory notes in Java and Go, followed by a generic template-method + simple-factory + strategy example.