Unified Modeling Language

UML is a language used to represent the classes and the relationship between them.

Shape
---
- positionX: int
---
+ render()

• - - private method/field
• + - public method/field

Types of relationship ​

It's kinda tricky to describe with text only 😅 It's fine for now tho.

Inheritance ​

Denoted with arrow (→)

The direction of the arrows head says what is the parent class.

public class Rectangle extends Shape {}
// Rectangle -> Shape

Composition ​

Denoted with diamond and arrow (◆→)

The class with diamond is composed of the class pointed by the arrow head).

public class Shape {

  private Size size;
}
// Shape ◆-> Size
// Car ◆-> Wheel

Aggregation ​

/* [...] */

Dependency relationship ​

Denoted with the dashed arrow (⇢).

Means that somewhere in one class we have a reference (a dependency) to another class, but it's not composed of that class.

public class Shape {

  public void render(Document doc) {
    // ...
  }
}
// Shape ---> Document