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From: Lawrence D'Oliveiro <ldo@geek-central.gen.new_zealand>
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Subject: =?UTF-8?B?QW5kcm9pZOKAlFdoeQ==?= Dalvik?
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The Android Builders Summit
<http://free-electrons.com/blog/abs-2011-videos/> had some interesting 
presentations, in particular Karim Yaghmour’s delving into the internals of 
Android, and Aleksander Gargenta’s “A Walk Through The Android Stack”.

From 48:00 onwards, Gargenta explains why Android uses the Dalvik VM instead 
of the Java VM.

* Why not Java SE? Too bloated, not suitable for low-power applications.
* Why not Java ME? Too expensive, everything runs in one VM => lousy 
security. And you don’t get the necessary hardware access.

Dalvik is purpose-built from the ground up; its .dex code is, even 
uncompressed, slightly smaller than a compressed .jar file. This simplifies 
class loading—a .apk file can be opened and mmap’d, and the code is ready 
for execution. (This is why zipalign is so important when building an 
Android app.)

Dalvik is also register-based, not stack based, for higher performance.