Cython vs J2ObjC

Cython is a free compiler for Python and the extended Cython language, used to create C extensions for Python. It translates source code into C or C++ that can be built as Python extension modules. Optional static type declarations can help produce more efficient C, while declared C and C++ types let Python code call existing C or C++ code. Cython supports source-level debugging across Python, Cython and C, and the project describes uses including wrapping external libraries, embedding CPython in applications and speeding up Python code with C modules. It can work with multidimensional NumPy arrays and integrate with low-level libraries and applications. Installation is available through pip, and some scientific Python distributions bundle it. A C compiler is required, with installation guidance for Linux, macOS and Windows. The project describes compatibility with major C and C++ compilers for CPython 3.8 and later, and characterizes PyPy support as mostly usable. Limited API and free-threading CPython support in Cython 3.1 are experimental. Cython is available under the Apache 2.0 License.

J2ObjC is Google’s free, open-source command-line tool for translating Java source code into Objective-C for iOS. It is designed for sharing non-UI application logic and data models across web, Android, and iOS projects. Supported Java features include exceptions, inner and anonymous classes, generics, threads, and reflection, and the tool can translate and execute JUnit tests. The distribution contains static libraries for Guava, JUnit, Mockito, Protocol Buffers, and other Java or Android utility libraries. J2ObjC does not provide a platform-independent UI toolkit; iOS interfaces use Objective-C, Objective-C++, or Swift with Apple’s iOS SDK. Developers need source code they own or are licensed to use because Android binaries cannot be converted. Requirements include a Mac workstation, macOS 15 or higher, Xcode 16 or higher, and JDK 21 or higher. The j2objcc script wraps clang and uses the iOS SDK, while Xcode projects need J2ObjC linker settings. Objective-C reference counting leaves memory management to developers.