The Dalvik VM is the older of the two runtimes. This compiler is referred to as the Java Android Compiler Kit or JACK for short.Īn outline of the new toolchain is as follows.įig 3.

The new toolchain attempts to simplify this process by providing a compiler that can compile the Java source code directly to dex bytecode. It does however mean the build process takes longer than it would if we were to compile straight to dex bytecode. The decoupling of both compilers has some implications, namely that anything that touts compatibility with Java (read, generates JVM compliant bytecode) can be used transparently with respect to dx. This is then packaged up with the various other resources into the apk container.

Bytecode transformers (see the Transformers API) then have an opportunity to manipulate the java bytecode to do things like obfuscation and minification (proguard, retrolamba, etc.) before finally being transcoded to dex bytecode by dx. This includes source generated by a Java annotation processor (think dagger, lombok etc.). Java source code is taken and converted to Java bytecode (.class files) via the Java compiler javac. This was the original toolchain released as part of the Android SDK. Overview of the Android Build System javac and dx The project has since been discontinued.įig 1. This can compile Java source code directly to machine code, and it therefore doesn’t require any JVM to execute. As an example, there was a compiler released as part of the GNU compiler collection called GCC-GCJ. That output can be anything the compiler supports via one of its backends, it doesn’t have to be JVM compliant bytecode. Any compiler that has a frontend for the spec can take that source code and produce output. Java, when referred to at this level is actually just a language spec. Usually when we say this we are talking about the programming language and in the typical case, the runtime environment is correctly inferred to be the Java Virtual Machine.

To answer this we must first clearly define what we mean by “Java”. So how much does Android rely on Java for building and running apps? This is often loosely and incorrectly interpreted to mean that Android apps execute on a standard Java Virtual Machine using standard Java bytecode. It is quite common knowledge that Android apps are developed in Java.

Use android studio as a java processor