This book is a collection of tutorial notes and sample codes written by the author while he was learning UML (Unified Modeling Language) himself. Main tutorials include: Introduction to UML; UML Class Diagrams; UML Activity Diagrams; UML Sequence Diagrams; UML State Machine Diagrams; UML Use Case Diagrams; Using LibreOffice and MS Visio to Draw UML Diagram. Updated in 2024 (Version v1.05) with minor changes. For latest updates and free sample chapters, visit https://www.herongyang.com/UML.