Tutorial: Using PlantUML for Class Diagrams

PlantUML is a simple yet powerful tool for creating class diagrams and other UML diagrams. It uses a plain-text language to define the diagram, making it accessible for developers familiar with text-based tools. This tutorial will walk you through the basics of creating class diagrams with PlantUML.

While you can install and use PlantUML locally, I suggest using an online IDE like PlantText (https://www.planttext.com).

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Add the following to begin:

@startuml
@enduml

All your diagram definitions go between @startuml and @enduml.

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Basic Syntax for Class Diagrams

1. Creating a Class

Define a class with its attributes and methods:

@startuml
class ClassName {
  + publicAttribute: Type
  - privateAttribute: Type
  # protectedAttribute: Type
  + publicMethod(): ReturnType
  - privateMethod(param: Type): ReturnType
}
@enduml

The result:

2. Relationships Between Classes

Define relationships such as inheritance, composition, etc.:

Example:

@startuml
class Parent
class Child
Parent <|-- Child : Inheritance
Parent *-- Child : Composition
Parent o-- Child : Aggregation
Parent -- Child : Association
Parent ..> Child : Dependency
@enduml

The result:

Example: Full Class Diagram

@startuml
package "University System" {
  class Student {
    + name: String
    + id: int
    + enroll(course: Course): void
  }
  class Course {
    + courseName: String
    + courseCode: String
    + addStudent(student: Student): void
  }
  class Professor {
    + name: String
    + teaches(course: Course): void
  }
  Student -- Course : "enrolls in"
  Professor -- Course : "teaches"
}
@enduml

The result:

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