Class diagram examples
UML class diagram examples generated from text
UML class diagram examples with attributes, methods, and inheritance — generated from plain English, no XML. Copy the prompt and make your own.
Prose in. Diagram out.
The prompt
An Animal has a name and can makeSound(). Dog and Cat inherit from Animal. A Shelter holds many Animals.
ChartCraft draws
More UML class diagram examples
Generated with ChartCraft and published in the examples gallery — open one to see its prompt, or use it as a starting point.
The notation, in 30 seconds
The UML class box and the five arrows that matter. Arrowheads carry the meaning — hollow triangle for “is-a”, diamonds for “owns”.
| Element | What it means |
|---|---|
| Class box | Three stacked compartments: name, attributes (name: type), methods (call()). |
| Inheritance (hollow triangle) | “Is-a”. Dog ▷ Animal. The triangle touches the parent. |
| Realization (dashed + triangle) | “Implements”. A class fulfilling an interface's contract. |
| Association (plain line) | “Knows about”. Add multiplicities at the ends: 1, 0..1, *. |
| Aggregation (hollow diamond) | “Has, but doesn't own” — parts survive the whole. Team ◇ Player. |
| Composition (filled diamond) | “Owns” — parts die with the whole. Order ◆ OrderLine. |
Best practices — and the classic mistakes
Do
- Model the domain, not the framework — leave controllers, DTOs, and helpers out unless the diagram is about them.
- Prefer composition arrows over inheritance when the relationship is “owns” rather than “is”.
- Put multiplicities on every association — 1, 0..1, or *; unlabelled lines invite wrong assumptions.
- Abstract classes in italics (or marked abstract) so readers know they're never instantiated.
- One diagram, one story: an inheritance view and an ownership view beat one diagram showing everything.
Avoid
- Inheritance used for code reuse (“Car extends Engine”) — that relationship is composition.
- Arrowheads swapped — the hollow triangle must touch the parent, diamonds touch the owner.
- Every private field and getter listed — the diagram becomes a code dump nobody reads.
- Missing multiplicities, leaving readers to guess whether a relationship is 1:1 or 1:many.
Questions
How were these UML class diagram examples made?
Each example was generated by ChartCraft from a plain-English prompt, then laid out automatically — the same way you'd make your own. Click any example to see its full page.
Can I use these UML class diagram examples as templates?
Yes — open an example, copy its prompt into the studio, then edit it in plain English to fit your case.
What's the difference between aggregation and composition?
Both are “has-a” diamonds. Composition (filled) means exclusive ownership — delete the Order and its OrderLines go with it. Aggregation (hollow) means the parts live independently — disband a Team and the Players remain.
Should every class in my codebase appear in the diagram?
No. A useful class diagram tells one story about the domain — 5 to 12 classes. Generate separate diagrams for separate subsystems rather than one wall-sized chart.
Is it free?
Your first 3 diagrams are free with no account, then 5 a month on a free account.