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There are several here: https://github.com/jashkenas/coffee-script/wiki/List-of-languages-that-compile-to-JS
Such as j2js, bicavm, doppio...(see the java section)
if your goal is to have users write Java in a browser and see it run, it makes.MUCH more sense to do the compiling and executing server side. A servlet could read the code, compile it and run it, then push the output back to the browser.
unless your thesis is "Anything that can be written in JavaScript will eventually be written in JavaScript."