WEBVTT

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So let's look at some of the details of Android runtime and the compilation process of an epic with

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a lifecycle diagram.

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Android apps are usually written in Java and compiled to Dalvik bytecode, which is somewhat different

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from the traditional Java bytecode.

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Dalvik bytecode is created by first compiling the Java code to class files and converting the JVM byte

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code to the Dalvik decs.

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Format with index tool.

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Dex, LPT does some optimizations on the text file and the result of Dex LPT is an oh Dex or optimized

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dex file.

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Then it's packaged into RPK files with a B.K. builder.

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So let's have a look at that, because RPK, it stands for Android Package Kit and also Android application

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package.

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So it's a file format that Android uses to distribute and install apps, it contains all of the elements

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that an app needs to install correctly on your device.

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So just like files on windows, you can place in APK file on your Android device to install an app.

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Oh, Dex files and Dex files were executed by Dalvik.

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Dalvik also uses Just in Time compilation, which was introduced in Android 2.0 to Froyo.

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Just in time, compilation adversely affects performance because compilation must be performed every

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time the app is executed.

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Now to improve performance since Android 5.0 Lollipop.

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Android executes this by code on the Android runtime or A.R.T..

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The Android system uses a tool called Decs to 08, which converts decs files into LTH files, which

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can be executed natively.

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So instead of having bytecode that is interpreted by a virtual machine and now has native code that

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will be executed natively by the processor.

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So this is called ahead of time or a Iot compilation.

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Now, as the name would imply, apps are pre compiled before they're executed for the very first time.

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This decompiled machine code is used for all subsequent executions.

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A improves performance by a factor of two while reducing power consumption.

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Art increases battery performance to such a large extent because of the AOT.

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So while Dalvik uses the Gitti or Gite approach, it results in much more battery utilization.

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So the key difference between Dalvik and art is the way the bytecode is executed.