Local variables must be copied to or from the operand stack by separate instructions. Standard Java bytecode executes 8-bit stack instructions.The constant pool has been modified to use only 32-bit indexes to simplify the interpreter.Unlike Java VMs, which are stack machines (stack-based architecture), the Dalvik VM is a register machine (register-based architecture).ĭalvik has some traits that differentiate it from other standard VMs: Instead, Java classes are compiled into a proprietary bytecode format and run on Dalvik (or compiled version thereof with newer ART), a specialized virtual machine (VM) designed for Android. Java bytecode in Java Archive ( JAR) files is not executed by Android devices. While most Android applications are written in Java-like language, there are some differences between the Java API and the Android API, and Android does not run Java bytecode by a traditional Java virtual machine (JVM), but instead by a Dalvik virtual machine in older versions of Android, and an Android Runtime (ART) in newer versions, that compile the same code that Dalvik runs to Executable and Linkable Format (ELF) executables containing machine code. This article compares the application programming interfaces (APIs) and virtual machines (VMs) of the programming language Java and operating system Android.
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