A Java to iOS Objective-C translation tool and runtime.
Java Objective-C C C++ Makefile Objective-C++ Other
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annotations Added Documented annotation to j2objc class annotations. Nov 22, 2017
cycle_finder Issue #965: fix public Eclipse class paths. Mar 30, 2018
doc Adds --no-wrapper-methods option to help users reduce code size. Jul 14, 2017
examples Added XCTest to avoid "empty test suite" TAP warning. We just need to… Apr 17, 2018
guava Removed j2objc flags specifying what is now default. Mar 13, 2017
inject/javax_inject Merged compiler warnings build refs, added -Wmissing-field-initialize… Dec 14, 2015
java_deps Removed asm build references, now that it is replaced by procyon. Nov 22, 2017
jre_emul Replaced wrapper method calls in native code with function calls. Apr 17, 2018
jsr305 Removed j2objc flags specifying what is now default. Mar 13, 2017
junit Removes test_junit_cycles from the top-level "make test". Apr 11, 2017
make Add watchOS simulator support Mar 8, 2018
protobuf Issue #963: Explicity reference the class type of fields in metadata … Mar 30, 2018
scripts Add watchOS simulator support Mar 8, 2018
testing Refactored mock support methods to reduce redundant code. Dec 16, 2017
translator Removed unused unused method, field and local variables in translator. Apr 17, 2018
tree_shaker Issue #965: fix public Eclipse class paths. Mar 30, 2018
xalan Issue #949: fixed reference cycles in Xalan's NamespaceMappings. Mar 7, 2018
.gitattributes Include git config files in public source. Jun 23, 2017
.gitignore Ignore IntelliJ IDEA files Dec 29, 2016
AUTHORS Deleted plain-text README. Feb 5, 2014
BUILD.dist Fixes the protobuf tests. Aug 16, 2017
CONTRIBUTING.md Updated README, added CONTRIBUTING page. Feb 5, 2014
INSTALL Update build requirements and tool links Dec 7, 2015
LICENSE Updated project files. Feb 4, 2014
Makefile Fixed race condition in public distribution build. Apr 18, 2018
README.md Removed references to Travis-CI build, now disabled. Jan 26, 2018
WORKSPACE.dist Adds a WORKSPACE and BUILD file to our distribution for Bazel support. Aug 16, 2017


J2ObjC: Java to Objective-C Translator and Runtime

Project site: http://j2objc.org
J2ObjC blog: http://j2objc.blogspot.com
Questions and discussion: http://groups.google.com/group/j2objc-discuss

What J2ObjC Is

J2ObjC is an open-source command-line tool from Google that translates Java source code to Objective-C for the iOS (iPhone/iPad) platform. This tool enables Java source to be part of an iOS application's build, as no editing of the generated files is necessary. The goal is to write an app's non-UI code (such as application logic and data models) in Java, which is then shared by web apps (using GWT), Android apps, and iOS apps.

J2ObjC supports most Java language and runtime features required by client-side application developers, including exceptions, inner and anonymous classes, generic types, threads and reflection. JUnit test translation and execution is also supported.

J2ObjC is currently beta quality. Several Google projects rely on it, but when new projects first start working with it, they usually find new bugs to be fixed. If you run into issues with your project, please report them!

What J2ObjC isn't

J2ObjC does not provide any sort of platform-independent UI toolkit, nor are there any plans to do so in the future. We believe that iOS UI code needs to be written in Objective-C, Objective-C++ or Swift using Apple's iOS SDK (Android UIs using Android's API, web app UIs using GWT, etc.).

J2ObjC cannot convert Android binary applications. Developers must have source code for their Android app, which they either own or are licensed to use.


  • JDK 1.8 or higher
  • Mac workstation or laptop
  • OS X 10.12 or higher
  • Xcode 8 or higher


This library is distributed under the Apache 2.0 license found in the LICENSE file with the following exceptions. The protocol buffers library is distributed under the same BSD license as Google's protocol buffers. See README and LICENSE.