Deze pagina was January 2017 voor het laatst geupdate

Read the new developers guide first.

Basic Guidelines and Coding Style

Most of the following should be common sense for anybody who has worked on open source or in a commercial programming envrionment. The following applies mostly to the main development branch i2p.i2p. Guidelines for other branches, plugins, and external apps may be substantially different; check with the appropriate developer for guidance.


  • Please don't just "write code". If you can, participate in other development activities, including: development discussions and support on IRC, zzz.i2p, and forum.i2p; testing; bug reporting and responses; documentation; code reviews; etc.
  • Active devs should be available periodically on IRC #i2p-dev. Be aware of the current release cycle. Adhere to release milestones such as feature freeze, tag freeze, and the checkin deadline for a release.

Release Cycle

Our normal release cycle is 6-10 weeks. Following are the approximate deadlines within a typical 8-week cycle. Actual deadlines for each release are set by the lead developer.

  • 1-2 days after previous release: Checkins to trunk are allowed.
  • 2-3 weeks after previous release: Deadline to propagate major changes from other branches to trunk.
  • 4-5 weeks before release: Deadline to request new home page links.
  • 3-4 weeks before release: Feature freeze. Deadline for major new features.
  • 2-3 weeks before release: Hold project meeting to review new home page link requests, if any.
  • 7-10 days before release: String freeze. No more changes to translated ("tagged") strings. Push strings to Transifex, announce translation deadline on Transifex.
  • 7-10 days before release: Feature deadline. Bug fixes only after this time. No more features, refactoring or cleanup.
  • 3-4 days before release: Translation deadline. Pull translations from Transifex and check in.
  • 2-3 days before release: Checkin deadline. No checkins after this time without the permission of the release builder.
  • Hours before release: Code review deadline.


  • Have a basic understanding of distributed source control systems, even if you haven't used monotone before. Ask for help if you need it. Once pushed, checkins are forever, there is no undo. Please be careful. If you have not used monotone before, start with baby steps. Check in some small changes and see how it goes.
  • Test your changes before checking them in. If you prefer the checkin-before-test development model, use your own development branch (e.g. i2p.i2p.yourname.test) and propagate back to i2p.i2p once it is working well. Do not break the build. Do not cause regressions. In case you do (it happens), please do not vanish for a long period after you push your change.
  • If your change is non-trivial, or you want people to test it and need good test reports to know whether your change was tested or not, add a checkin comment to history.txt and increment the build revision in
  • Ensure that you have the latest monotonerc file in _MTN. Do not check in on top of untrusted revisions.
  • Ensure that you 'mtn pull' and 'mtn update' to the latest revision before you check in and push. If you inadvertently diverge, merge and push as soon as possible. Don't routinely make others merge for you. Yes, we know that monotone says you should push and then merge, but in our experience, in-workspace merge works just as well as in-database merge, without creating a merge revision.
  • Do not check in major changes into the main i2p.i2p branch late in the release cycle. If a project will take you more than a couple days, create your own branch in monotone and do the development there so you do not block releases.

Coding Style

  • Coding style throughout most of the code is 4-spaces for indentation. Do not use tabs. Do not reformat code. If your IDE or editor wants to reformat everything, get control of it. Yes, we know 4 spaces is a pain, but perhaps you can configure your editor appropriately. In some places, the coding style is different. Use common sense. Emulate the style in the file you are modifying.
  • All new public and package-private classes and methods require Javadocs. Add @since release-number. Javadocs for new private methods are desirable.
  • For any Javadocs added, there must not be any doclint errors or warnings. Run 'ant javadoc' with Oracle Java 8 or higher to check. All params must have @param lines, all non-void methods must have @return lines, all exceptions declared thrown must have @throws lines, and no HTML errors.
  • Classes in core/ (i2p.jar) and portions of i2ptunnel are part of our official API. There are several out-of-tree plugins and other applications that rely on this API. Be careful not to make any changes that break compatibility. Don't add methods to the API unless they are of general utility. Javadocs for API methods should be clear and complete. If you add or change the API, also update the documentation on the website (i2p.www branch).
  • Tag strings for translation where appropriate. Don't change existing tagged strings unless really necessary, as it will break existing translations. Do not add or change tagged strings after the "tag freeze" in the release cycle so that translators have a chance to update before the release.
  • Use generics and concurrent classes where possible. I2P is a highly multi-threaded application.
  • Be familiar with common Java pitfalls that are caught by findbugs. Run 'ant findbugs' to learn more.
  • We require Java 7 to build and run I2P. Do not use Java 8 classes or methods anywhere. Do not use Java 7 or 8 classes or methods in embedded subsystems (core, router, mstreaming, streaming, i2ptunnel), as Android and embedded applications require only Java 6. All classes must be available in Android API 9. Java 7 language features are acceptable in these subsystems if supported by the current version of the Android SDK and they compile to Java 6-compatible code.
  • Explicitly convert between primitive types and classes; don't rely on autoboxing/unboxing.
  • Don't use URL. Use URI.
  • Don't catch Exception. Catch RuntimeException and checked exceptions individually.
  • Don't use String.getBytes() without a UTF-8 charset argument. You may also use DataHelper.getUTF8() or DataHelper.getASCII().
  • Always specify a UTF-8 charset when reading or writing files. The DataHelper utilities may be helpful.
  • Always specify a locale (for example Locale.US) when using String.toLowerCase() or String.toUpperCase(). Do not use String.equalsIgnoreCase(), as a locale cannot be specified.
  • Don't use String.split(). Use DataHelper.split().
  • Ensure that InputStreams and OutputStreams are closed in finally blocks.
  • Use {} for all for and while blocks, even if only one line. If you use {} for either the if, else, or if-else block, use it for all blocks. Put "} else {" on a single line.
  • Specify fields as final wherever possible.
  • Don't store I2PAppContext, RouterContext, Log, or any other references to router or context items in static fields.
  • Don't start threads in constructors. Use I2PAppThread instead of Thread.


  • Only check in code that you wrote yourself. Before checking in any code or library jars from other sources, justify why it is necessary, verify the license is compatible, and obtain approval from the lead developer.
  • If you do obtain approval to add external code or jars, and binaries are available in any Debian or Ubuntu package, you must implement build and packaging options to use the external package instead. Checklist of files to modify:, build.xml, debian/control, debian/i2p-router.install, debian/i2p-router.links, debian/rules, sub-build.xml
  • For any images checked in from external sources, it is your responsibility to first verify the license is compatible. Include the license and source information in the checkin comment.


  • Managing Trac tickets is everybody's job, please help. Monitor for tickets you have been assigned or can help with. Assign, categorize, comment on, fix, or close tickets if you can.
  • New developers should start by fixing a bug. Search for bugs with the 'easy' keyword on trac. When you have a fix, attach your patch to the ticket and add the keyword 'review-needed'. Do not close the ticket until it's been successfully reviewed and you've checked your changes in. Once you've done this smoothly for a couple of tickets, you may follow the normal procedure below.
  • Close a ticket when you think you've fixed it. We don't have a test department to verify and close tickets. If you arent sure you fixed it, close it and add a note saying "I think I fixed it, please test and reopen if it's still broken". Add a comment with the dev build number or revision and set the milestone to the next release.