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A JVM in TypeScript.

doppio: A JVM in TypeScript

doppio is a double shot of espresso. In this case it's also a JVM written in TypeScript.

To try doppio now, head to the live demo page.

To learn more, head to the doppio wiki.

You can also get in touch via our mailing list or via the IRC channel #plasma-umass on Freenode.

Getting & Building the Code

Before attempting to build doppio, you must have the following installed:

  • Node v0.10 or higher
  • NPM packages grunt-cli and bower installed globally
    • npm install -g grunt-cli bower
  • Java 6 JDK

If you are on Windows, you will need the following installed:

  • Git (must be on your PATH)
  • Python (must be on your PATH)
  • A version of Visual Studio

Run the following commands to build doppio. Note that your first time building may take some time, as the build script will download the entire Java Class Library.

git clone
cd doppio
npm install
bower install
grunt release


To run doppio on localhost:

grunt dev
tools/ --dev

To get the optimized release version:

grunt release
tools/ --release

Then point your browser to http://localhost:8000/.

To include your own code in the browser without manually uploading each file, place your .class files in a directory under classes/, then re-run grunt dev or grunt release to re-generate the listings.json file.

For example:

#in shell
cp -ivR /path/to/my/class/files/ classes/my-classes/

#in browser
java -cp /sys/classes/my-classes my/package/MyClass

You can also run JAR files in the browser, e.g.:

java -jar /path/to/jar.jar
# Or if you don't want to run the JAR file's main class...
java -cp /path/to/jar.jar package.MyClass

doppio can also be run from the console. For example:

grunt dev-cli
node build/dev-cli/console/disassembler.js classes/demo/Fib
# doppio-dev -> node build/dev/console/runner.js
./doppio-dev classes/demo/Fib
./doppio-dev classes/demo/Fib 7        # pass an argument to the JVM
./doppio-dev -jar my_application.jar   # extract and run a JAR

To get the optimized version, use grunt release-cli. The build products can be found in build/release-cli, and the runtime can be invoked via ./doppio.

Automated Rebuilding

To automatically rebuild doppio while you modify files, run the following command:

grunt release watch

This will perform a complete build of doppio, and then will watch files to trigger partial rebuilds.

Running Tests

Run all tests:

grunt test

Run a specific test, or test with different options:

node build/dev-cli/console/test_runner.js -h
node build/dev-cli/console/test_runner.js classes/test/Strings
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