The document discusses how Kotlin and desugaring tools like D8 help support Java 8 language features on Android, allowing faster builds, smaller app sizes, and better performance. It covers how Kotlin and tools like D8 compile code using Java 8 features to dex files, explaining challenges earlier tools had. Desugaring allows lambda expressions, default methods and more to work on older Android versions by transforming bytecode. The document recommends using Kotlin which provides the same features and compiles them the same way as desugaring tools.

2. What We Concern?
Faster Build Time
More Productivity
Smaller APK size
Benefits Users and Product
Run Time Performance

3. Closer Look at Android Run Time
Kotlin source
code
(.kt)
Kotlin compiler

4. (JIT)
Compiler
(AoT)

5. Android Studio does not support all Java 8 language features,
Supported Java 8 language features and APIs
https://developer.android.com/studio/write/java8-support

6. Desugaring History
Goal : Allow newer language features to run on all devices
https://android-developers.googleblog.com/2014/12/hello-world-meet-our-new-experimental.html
Jack &Jil ToolChain
 Transforms .java to .dex
 Supports lambda functions & method refs all
android versions.
 Supports Android API 26+
 Does not support java.time.*
 Failed to convert to .dex directly with no bytecode
in between.
 Slow in compilation

7. RetroLambda
Back Support of Java 8’s lambda expressions to Java 7,6 and 5.

8. class Java8 {
interface Logger {
void log(String s);
}
public static void main(String... args) {
sayHi(s -> System.out.println(s));
}
private static void sayHi(Logger logger) {
logger.log("Hello!");
}
}
$ javac *.java
$ ls
Java8.java Java8.class Java8$Logger.class
$ $ANDROID_HOME/build-tools/28.0.2/dx --dex --output . *.class Uncaught translation error:
com.android.dx.cf.code.SimException:
ERROR in Java8.main:([Ljava/lang/String;)V: invalid opcode ba - invokedynamic requires --min-sdk-version
>= 26 (currently 13)
1 error; aborting
Sample class

9. Button button = (Button)findViewById(R.id.button);
button.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
Toast.makeText(this, "Button clicked",
Toast.LENGTH_LONG).show();
}
});
without lambda expression
with lambda expressions
Button button = (Button)findViewById(R.id.button);
button.setOnClickListener(v -> Toast.makeText(this, "Button
clicked", Toast.LENGTH_LONG).show());

10. D8 Dexer
 Replacement for Dx.
 Faster Compared to Dx.
 Reducing build time and generated small apk size.
 Optimised .dex means more performance.
https://android-developers.googleblog.com/2017/08/next-generation-dex-compiler-now-in.html

11. Default toolchain desugaring
D8 integrated desugaring

12. Just Use Kotlin

13.  Provides Lambdas
 Method references
 Default and static (-Like) functions on interfaces
 Source transformation
 All of those features are actually implemented by kotlinc is exactly same way that D8
desugars the java 8 byte code
Increases team efficiency
Complies with existing Java code
Easily maintainable
Less buggy
Reduced mobile app development cost
Safe and secure

14. Resources
 https://developer.android.com/studio/write/java8-support
 https://android-developers.googleblog.com/2017/08/next-generation-dex-compiler-now-in.html
 https://law.justia.com/cases/federal/appellate-courts/cafc/17-1118/17-1118-2018-03-27.html (Google vs Oracle copy right case)
 https://android-developers.googleblog.com/2017/04/java-8-language-features-support-update.html
 https://jakewharton.com/androids-java-8-support/
 https://pusher.com/state-of-kotlin#kotliners
 https://insights.stackoverflow.com/survey/2018/
 https://kotlinlang.org/docs/reference/faq.html
 https://www.appbrain.com/stats/libraries/details/kotlin/kotlin

15. 15
THANK YOU
Phani Gullapalli