Desugaring in Android for Backward Compatibility
How Desugaring Lets You Use Modern Java on Legacy Android
Desugaring in Android is a compilation process that transforms newer Java language features and APIs into equivalent code that can run on older Android versions. Because of this, we all can use modern Java features and APIs while maintaining backward compatibility.
Why is it needed?
Older Android devices use older versions of the Android Runtime (ART or Dalvik) that do not support features from newer Java versions (like Java 8+). However, many developers want to use modern Java features without dropping support for older Android versions.
Desugaring helps bridge this gap.
Few examples of the new Java Language features/APIs that it handles:
Lambda expressions (() -> {})
Method references (ClassName::method)
Try-with-resources statements
Time API (java . time . *)
Stream API (java . util . stream)
How to enable it?
Enable core library desugaring - Set coreLibraryDesugaringEnabled to true in compileOptions
Set Java version compatibility - Configure both sourceCompatibility and targetCompatibility to JavaVersion . VERSION_1_8 or higher
Add desugaring dependency - Include coreLibraryDesugaring 'com . android . tools : desugar_jdk_libs : version'
How does it work?
The Android Gradle Plugin performs desugaring during compilation by:
Analyzing bytecode to identify newer language constructs
Transforming syntax into equivalent older Java code
Adding compatibility libraries for newer APIs
[Kotlin Code] ─▶ [Kotlin Compiler] ─▶ [Java Bytecode] ─▶ [D8 / R8 Compiler](Desugar Language Features, Desugar Library APIs) ─▶ [DEX Bytecode] ─▶ [Runs on all Android]
Note: Kotlin doesn't eliminate the need for desugaring as it still uses Java features under the hood and relies on Java APIs that may not be supported on older Android versions, so it needs desugaring for compatibility.
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Thanks
Amit Shekhar
Founder, Outcome School