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Architecture
Being optimized for low memory requirements, Dalvik has some specific characteristics that differentiate it from other standard VMs[4]:
- The VM was slimmed down to use less space. The underlying C standard library was rewritten, and the C++ implementation has no support for Exception handling,
- Dalvik has no Just-in-time compiler
- The constant pool has been modified to use only 32-bit indexes to simplify the interpreter.
Dalvik uses Apache Harmony (which is under the Apache License) instead of OpenJDK (which is under the GPL + linking exception) to allow cell phone makers to modify the core VM without having to distribute their code.
Relationship to Java
Dalvik is often referred to as a Java Virtual Machine, but this is not strictly accurate, as the bytecode on which it operates is not Java bytecode. Instead, a tool named dx, included in the Android SDK, transforms the Java Class files of Java classes compiled by a regular Java compiler into another class file format (the .dex format).[5]
References
- ^ "What is Android?". code.google.com. Retrieved on 2008-02-05.
- ^ Journal entry
- ^ "Google Calling: Inside Android, the gPhone SDK". onlamp.com. Retrieved on 2008-02-05.
- ^ Rose, John (2008-05-31). "with Android and Dalvik at Google I/O". Retrieved on 2008-06-08.
- ^ "What is Android?: Android Runtime". Google (2007-11-12). Retrieved on 2007-11-13. "The Dalvik VM executes files in the Dalvik Executable (.dex) format which is optimized for minimal memory footprint. The VM is register-based, and runs classes compiled by a Java language compiler that have been transformed into the .dex format by the included "dx" tool."
External links
- Dalvik: how Google routed around Sun's IP-based licensing restrictions on Java ME
- Google and Sun may butt heads over Android
- Dex File Format
- The town of Dalvik celebrates its namesake
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