Java Design Patterns: A Java Learning Reference
/java-design-patterns
Java Design Patterns is a large, community-maintained catalog of Gang-of-Four and other design patterns implemented as commented, runnable Java code instead of described in prose. Reach for it when you want to see a pattern working end to end in real Java rather than a UML diagram; skip it if you need patterns written in a language other than Java, since every example here is Java only.
What is Java Design Patterns?
Java Design Patterns is a GitHub repository and companion website that shows classic software design patterns as working Java code instead of textbook diagrams. Each pattern lives in its own folder with commented source, and the README says you can browse everything by pattern name, by tag, or by category.
What the Collection Covers
- โPatterns are browsable three ways per the README: by searching for a specific name, by tag such as Performance, Gang of Four, or Data access, or by category such as Creational and Behavioral.
- โSource code for every pattern is commented well enough to double as a short tutorial on implementing it, according to the README.
- โA separate Software Design Principles page at java-design-patterns.com/principles/ covers ideas like KISS, YAGNI, and keeping a solution as simple as it can possibly be, before you touch a single pattern.
- โThe full list of implemented patterns is browsable separately at java-design-patterns.com/patterns/, outside the GitHub repo itself.
- โAn optional companion e-book, 'Open Source Java Design Patterns,' is sold on Payhip for readers who want it in book form.
- โGitHub topics on the repo include design-patterns, java, principles, snippets-collection, and hacktoberfest, tying it to that annual contribution event.
- โContribution paths include a developer wiki, a Gitter chatroom for questions, and GitHub issues for requesting a pattern that's missing.
Who Benefits from This Resource?
Java Design Patterns suits Java developers who want to turn a pattern's name into working code fast, plus students or interview candidates who learn better from runnable examples than from UML diagrams. It's a weaker fit if you don't write Java. The README documents implementations in Java alone, even though the README text itself is translated into many languages.
Strengths
- โEvery pattern ships as commented, runnable Java rather than pseudocode, so you can see the trade-offs in real syntax.
- โThree ways to browse (by name, by tag, or by category), per the README, make it easier to find a pattern when you don't already know its name.
- โA companion Software Design Principles page primes you with KISS and YAGNI before you dive into individual patterns, context most pattern catalogs skip.
- โMIT license keeps the code free to reuse.
- โCarries the hacktoberfest GitHub topic, suggesting contribution activity picks up around that yearly event.
Considerations and Scope
- โณExamples are Java only. The README's list of translated languages covers the documentation and README text, not implementations in other programming languages.
- โณThe README groups patterns into 'Creational, Behavioral, and others' without laying out a full category taxonomy in one place.
- โณNo version number, changelog, or last-updated date appears in the README, so there's no documented way to gauge how current any specific pattern's code is.
- โณThe companion e-book is a paid product outside the repository, and getting a free copy requires already having a merged pull request, not just being a reader.
- โณInstall and usage steps aren't documented, since this is a reference site meant for reading and browsing rather than a library you add as a dependency.
Other Design Pattern Resources
Frequently Asked Questions
Java Design Patterns is released under the MIT license, as stated in the repository's README.
Java Design Patterns takes contributions: the project points you to a developer wiki and a Gitter chatroom for questions, and you can open a GitHub issue to request a pattern that isn't covered yet.
It's normally a paid e-book sold on Payhip, though the README says contributors with an accepted pull request can request a free copy by emailing the maintainer with their GitHub username and PR link.
The pattern implementations are Java only. What's translated is the documentation: the README links to README versions in languages including Chinese, Korean, French, Arabic, Spanish, Portuguese, Russian, German, Japanese, and Vietnamese, among others.
The README doesn't list specific frameworks or library versions. It only says the examples rely on established, widely used open-source Java tooling, without naming exact ones.
Java Design Patterns links to a dedicated Software Design Principles page at java-design-patterns.com/principles/, covering ideas like KISS and YAGNI that the README recommends understanding before the patterns themselves.
Best use cases
- โขLooking up a specific pattern by name when you already know what you need (Singleton, Observer, Strategy) and want working Java instead of a diagram.
- โขPrepping for a system-design or OOP interview where you need to explain a pattern's trade-offs, not just recite its definition.
- โขTeaching a Java course or onboarding juniors, using the commented source as a walkthrough instead of writing example code from scratch.
- โขBrowsing by category or tag (Performance, Data access, Gang of Four) when you're not sure which pattern fits your problem yet.
Related repositories
Still deciding about java-design-patterns?
One click hands the question to an AI along with this page โ see what it says about java-design-patterns.