If you have a compiled Java class file (MyClass.class), you can convert it to classes.dex:
java -jar d8.jar MyClass.class
Output: A file named classes.dex in the current directory.
Once you have the file, run it with Java (requires JDK 8 or higher):
java -jar /path/to/d8.jar [options] input1.class input2.class ...
Historically, Android used a tool called DX (Dalvik Executable) to convert Java .class files into the .dex (Dalvik Executable) format that runs on Android’s virtual machine (first Dalvik, then ART). The DX tool was located inside dx.jar.
With Android Studio 3.0 and later, Google introduced D8 as a replacement for DX. D8 is faster, produces smaller .dex files, and supports modern Java language features (including Java 8+). The core of this tool is packaged inside d8.jar. d8.jar download
Key takeaway:
d8.jaris the executable archive that contains the D8 compiler and its dependencies.
Once you have d8.jar, you can invoke it via command line or programmatically.
If you trust the official Maven repository, here’s a direct pattern:
https://repo1.maven.org/maven2/com/android/tools/build/d8/8.2.0/d8-8.2.0.jar
Replace 8.2.0 with the latest version. Always verify the SHA-256 checksum from the repository metadata. If you have a compiled Java class file ( MyClass
Unlike standard executable tools, d8.jar is a Java archive. You must run it using the Java Runtime Environment (JRE).
Google open-sourced R8 (which contains d8). You can build it yourself:
https://github.com/r8-keep/r8
Build with:
git clone https://github.com/r8-keep/r8.git
cd r8
tools/gradle.py d8
Output will be in build/libs/d8.jar
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Subject: How to correctly download and setup d8.jar
A lot of users run into broken links when trying to download d8.jar explicitly. Here is the correct way to get it working on your machine.
Method 1: Android SDK (Recommended)
The d8 tool is part of the Android Build Tools. Output: A file named classes
Method 2: Command Line (SDK Manager)
If you are on a headless server or CI environment:
sdkmanager "build-tools;34.0.0"
(Replace 34.0.0 with your desired version)