The GNU Compiler for Java (GCJ) is a compiler for the Java programming language that is part of the GNU Compiler Collection (GCC). It can compile Java source code to either Java Virtual Machine bytecode, or directly to machine code for any of a number of CPU architectures. It can also compile class files containing bytecode or entire Java archives (JARs) containing such class files into machine code. Almost all of the runtime library used by GCJ comes from the GNU Classpath project. A diagram of the operation of an ideal compiler. ... Java is a reflective, object-oriented programming language developed initially by James Gosling and colleagues at Sun Microsystems. ... The GNU Compiler Collection (usually shortened to GCC) is a set of programming language compilers produced by the GNU Project. ... Source code (commonly just source or code) is any series of statements written in some human-readable computer programming language. ... A Java Virtual Machine or JVM is a virtual machine that runs Java byte code. ... Byte-code is a sort of intermediate code that is more abstract than machine code. ... A system of codes directly understandable by a computers CPU is termed this CPUs native or machine language. ... To a large extent, the design of a CPU, or central processing unit, is the design of its control unit. ... Class files contain bytecodes for the Java Virtual Machine. ... In computing, a Jar file (short for Java ARchive) is a ZIP file used to distribute a set of Java classes. ... GNU Classpath is an attempt to create a free implementation of the standard class library for Java. ...

CNI (Compiled Native Interface)

The Compiled Native Interface (CNI) is a software framework for the GNU GCJ compiler which allows Java code to call and be called by native applications (programs specific to a hardware and operating system platform) and libraries written in C++. This article needs cleanup. ... The GNU logo, drawn by Etienne Suvasa GNU is a recursive acronym for GNUs Not Unix. The GNU project was announced in 1983 by Richard Stallman with the goal of creating a complete UNIX-compatible operating system -- called the GNU system or simply GNU -- that is free software, meaning... A diagram of the operation of an ideal compiler. ... Java is a reflective, object-oriented programming language developed initially by James Gosling and colleagues at Sun Microsystems. ... C++ (pronounced see plus plus, IPA: /siː pləs pləs/) is a general-purpose computer programming language. ...

It is similar to the Java Native Interface (JNI) framework which comes as standard with various Java virtual machines. However the CNI authors claim various advantages over JNI: [1] The Java Native Interface (JNI) is a programming framework that allows Java code running in the Java virtual machine (VM) to call and be called by native applications (programs specific to a hardware and operating system platform) and libraries written in other languages, such as C, C++ and assembly. ... A Java Virtual Machine or JVM is a virtual machine that runs Java byte code. ...

We use CNI because we think it is a better solution, especially for a Java implementation that is based on the idea that Java is just another programming language that can be implemented using standard compilation techniques. Given that, and the idea that languages implemented using Gcc should be compatible where it makes sense, it follows that the Java calling convention should be as similar as practical to that used for other languages, especially C++, since we can think of Java as a subset of C++. CNI is just a set of helper functions and conventions built on the idea that C++ and Java have the *same* calling convention and object layout; they are binary compatible. (This is a simplification, but close enough.)

Support for AWT and Swing

Currently, GCJ does not fully support Java's two graphical APIs: AWT and Swing. An application run using the GCJ runtime environment will not work properly if it utilizes either of these APIs. Full support for both AWT and Swing is currently in progress. In the meantime, GUI applications should be run using the offical runtime provided by Sun Microsystems.. API redirects here. ... The Abstract Windowing Toolkit (AWT) is Javas platform_independent windowing, graphics, and user_interface widget toolkit. ... Swing is a GUI toolkit for Java. ... Sun Microsystems (Sun Microsystems, Inc. ...

See also

• GIJ
• GNU Classpath
• Kaffe
• SableVM
• Jikes

The GNU Interpreter for Java (GIJ) is a Java bytecode interpreter for the Java programming language. ... GNU Classpath is an attempt to create a free implementation of the standard class library for Java. ... Kaffe is a clean room design of the Java virtual machine. ... SableVM is a clean room implementation of Java bytecode interpreter implementing the Java virtual machine specification, second edition. ... In computing, a Java compiler is a computer program that translates programs in Java to Java byte-code. ...

External links

• GCJ Homepage
• GCJ Manual
• http://gcc.gnu.org/onlinedocs/gcj/About-CNI.html - 'About CNI' section of GCJ Manual
• http://gcc.gnu.org/java/faq.html - GCJ Frequently Asked Questions