Design Patterns Implemented in Java

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Introduction

Design patterns are the best, formalized practices a programmer can use to solve common problems when designing an application or system.

Design patterns can speed up the development process by providing tested, proven development paradigms.

Reusing design patterns helps prevent subtle issues that cause major problems, and it also improves code readability for coders and architects who are familiar with the patterns.

Getting Started

This site showcases Java Design Patterns. The solutions have been developed by experienced programmers and architects from the open-source community. The patterns can be browsed by their high-level descriptions or by looking at their source code. The source code examples are well commented and can be thought of as programming tutorials on how to implement a specific pattern. We use the most popular battle-proven open-source Java technologies.

Before you dive into the material, you should be familiar with various Software Design Principles.

All designs should be as simple as possible. You should start with KISS, YAGNI, and Do The Simplest Thing That Could Possibly Work principles. Complexity and patterns should only be introduced when they are needed for practical extensibility.

Once you are familiar with these concepts you can start drilling down into the available design patterns by any of the following approaches:

Search for a specific pattern by name. Can't find one? Please report a new pattern here.
Using tags such as Performance, Gang of Four or Data access.
Using pattern categories, Creational, Behavioral, and others.

Hopefully, you find the object-oriented solutions presented on this site useful in your architectures and have as much fun learning them as we had while developing them.

How to Contribute

If you are willing to contribute to the project you will find the relevant information in our developer wiki. We will help you and answer your questions in the Gitter chatroom.

The Book

The design patterns are now available as an e-book. Find out more about "Open Source Java Design Patterns" here: https://payhip.com/b/kcaF9

The project contributors can get the book for free. Contact the maintainer via Gitter chatroom or email (iluwatar (at) gmail (dot) com ). Send a message that contains your email address, Github username, and a link to an accepted pull request.

License

This project is licensed under the terms of the MIT license.

Contributors

<table> <tbody> <tr> <td align="center" valign="top" width="16.66%"><a href="https://github.com/iluwatar"><img src="https://avatars1.githubusercontent.com/u/582346?v=4?s=100" width="100px;" alt="Ilkka Seppälä"/> Ilkka Seppälä</a> <a href="#projectManagement-iluwatar" title="Project Management">📆</a> <a href="#maintenance-iluwatar" title="Maintenance">🚧</a> <a href="#content-iluwatar" title="Content">🖋</a></td> <td align="center" valign="top" width="16.66%"><a href="http://subho.xyz"><img src="https://avatars0.githubusercontent.com/u/13291222?v=4?s=100" width="100px;" alt="Subhrodip Mohanta"/> Subhrodip Mohanta</a> <a href="https://github.com/iluwatar/java-design-patterns/commits?author=ohbus" title="Code">💻</a> <a href="https://github.com/iluwatar/java-design-patterns/pulls?q=is%3Apr+reviewed-by%3Aohbus" title="Reviewed Pull Requests">👀</a> <a href="#maintenance-ohbus" title="Maintenance">🚧</a></td> <td align="center" valign="top" width="16.66%"><a href="https://github.com/amit1307"><img src="https://avatars0.githubusercontent.com/u/23420222?v=4?s=100" width="100px;" alt="amit1307"/> amit1307</a> <a href="https://github.com/iluwatar/java-design-patterns/commits?author=amit1307" title="Code">💻</a></td> <td align="center" valign="top" width="16.66%"><a href="https://github.com/npathai"><img src="https://avatars2.githubusercontent.com/u/1792515?v=4?s=100" width="100px;" alt="Narendra Pathai"/> Narendra Pathai</a> <a href="https://github.com/iluwatar/java-design-patterns/commits?author=npathai" title="Code">💻</a> <a href="#ideas-npathai" title="Ideas, Planning, & Feedback">🤔</a> <a href="https://github.com/iluwatar/java-design-patterns/pulls?q=is%3Apr+reviewed-by%3Anpathai" title="Reviewed Pull Requests">👀</a></td> <td align="center" valign="top" width="16.66%"><a href="https://github.com/fluxw42"><img src="https://avatars1.githubusercontent.com/u/1545460?v=4?s=100" width="100px;" alt="Jeroen Meulemeester"/> Jeroen Meulemeester</a> <a href="https://github.com/iluwatar/java-design-patterns/commits?author=fluxw42" title="Code">💻</a></td> <td align="center" valign="top" width="16.66%"><a href="http://www.joemccarthy.co.uk"><img src="https://avatars0.githubusercontent.com/u/4526195?v=4?s=100" width="100px;" alt="Joseph McCarthy"/> Joseph McCarthy</a> <a href="https://github.com/iluwatar/java-design-patterns/commits?author=mikulucky" title="Code">💻</a></td> </tr> <tr> <td align="center" valign="top" width="16.66%"><a href="https://github.com/thomasoss"><img src="https://avatars1.githubusercontent.com/u/22516154?v=4?s=100" width="100px;" alt="Thomas"/> Thomas</a> <a href="https://github.com/iluwatar/java-design-patterns/commits?author=thomasoss" title="Code">💻</a></td> <td align="center" valign="top" width="16.66%"><a href="https://github.com/anuragagarwal561994"><img src="https://avatars1.githubusercontent.com/u/6075379?v=4?s=100" width="100px;" alt="Anurag Agarwal"/> Anurag Agarwal</a> <a href="https://github.com/iluwatar/java-design-patterns/commits?author=anuragagarwal561994" title="Code">💻</a></td> <td align="center" valign="top" width="16.66%"><a href="https://markusmo3.github.io"><img src="https://avatars1.githubusercontent.com/u/3317416?v=4?s=100" width="100px;" alt="Markus Moser"/> Markus Moser</a> <a href="#design-markusmo3" title="Design">🎨</a> <a href="https://github.com/iluwatar/java-design-patterns/commits?author=markusmo3" title="Code">💻</a> <a href="#ideas-markusmo3" title="Ideas, Planning, & Feedback">🤔</a></td> <td align="center" valign="top" width="16.66%"><a href="https://twitter.com/i_sabiq"><img src="https://avatars1.githubusercontent.com/u/19510920?v=4?s=100" width="100px;" alt="Sabiq Ihab"/> Sabiq Ihab</a> <a href="https://github.com/iluwatar/java-design-patterns/commits?author=isabiq" title="Code">💻</a></td> <td align="center" valign="top" width="16.66%"><a href="http://inbravo.github.io"><img 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href="https://github.com/Crossy147"><img src="https://avatars2.githubusercontent.com/u/7272996?v=4?s=100" width="100px;" alt="Kamil Pietruszka"/> Kamil Pietruszka</a> <a href="https://github.com/iluwatar/java-design-patterns/commits?author=Crossy147" title="Code">💻</a></td> <td align="center" valign="top" width="16.66%"><a href="http://cs.joensuu.fi/~zkhayda"><img src="https://avatars2.githubusercontent.com/u/660742?v=4?s=100" width="100px;" alt="Zafar Khaydarov"/> Zafar Khaydarov</a> <a href="https://github.com/iluwatar/java-design-patterns/commits?author=zafarella" title="Code">💻</a> <a href="https://github.com/iluwatar/java-design-patterns/commits?author=zafarella" title="Documentation">📖</a></td> <td align="center" valign="top" width="16.66%"><a href="https://kemitix.github.io/"><img src="https://avatars1.githubusercontent.com/u/1147749?v=4?s=100" width="100px;" alt="Paul Campbell"/> Paul Campbell</a> <a href="https://github.com/iluwatar/java-design-patterns/commits?author=kemitix" title="Code">💻</a></td> <td align="center" valign="top" width="16.66%"><a href="https://github.com/Argyro-Sioziou"><img src="https://avatars0.githubusercontent.com/u/22822639?v=4?s=100" width="100px;" alt="Argyro Sioziou"/> Argyro Sioziou</a> <a href="https://github.com/iluwatar/java-design-patterns/commits?author=Argyro-Sioziou" title="Code">💻</a></td> <td align="center" valign="top" width="16.66%"><a href="https://github.com/TylerMcConville"><img src="https://avatars0.githubusercontent.com/u/4946449?v=4?s=100" width="100px;" alt="TylerMcConville"/> TylerMcConville</a> <a href="https://github.com/iluwatar/java-design-patterns/commits?author=TylerMcConville" title="Code">💻</a></td> </tr> <tr> <td align="center" valign="top" width="16.66%"><a href="https://github.com/saksham93"><img src="https://avatars1.githubusercontent.com/u/37399540?v=4?s=100" width="100px;" alt="saksham93"/> saksham93</a> <a href="https://github.com/iluwatar/java-design-patterns/commits?author=saksham93" title="Code">💻</a></td> <td align="center" valign="top" width="16.66%"><a href="https://github.com/nikhilbarar"><img src="https://avatars2.githubusercontent.com/u/37332144?v=4?s=100" width="100px;" alt="nikhilbarar"/> nikhilbarar</a> <a href="https://github.com/iluwatar/java-design-patterns/commits?author=nikhilbarar" title="Code">💻</a></td> <td align="center" valign="top" width="16.66%"><a href="http://colinbut.com"><img src="https://avatars2.githubusercontent.com/u/10725674?v=4?s=100" width="100px;" alt="Colin But"/> Colin But</a> <a href="https://github.com/iluwatar/java-design-patterns/commits?author=colinbut" title="Code">💻</a></td> <td align="center" valign="top" width="16.66%"><a href="https://github.com/ruslanpa"><img src="https://avatars2.githubusercontent.com/u/1503411?v=4?s=100" width="100px;" alt="Ruslan"/> Ruslan</a> <a href="https://github.com/iluwatar/java-design-patterns/commits?author=ruslanpa" title="Code">💻</a></td> <td align="center" valign="top" width="16.66%"><a