gistfile1.txt

~/projects/jruby ➔ cat blah.rb
class MyClass
  def foo
    puts 'hello'
  end
end

~/projects/jruby ➔ jrubyc --javac blah.rb
Generating Java class MyClass to /Users/headius/projects/jruby/MyClass.java
javac  -d /Users/headius/projects/jruby -cp /Users/headius/projects/jruby/lib/jruby.jar:. /Users/headius/projects/jruby/MyClass.java

~/projects/jruby ➔ javap MyClass
Compiled from "MyClass.java"
public class MyClass extends org.jruby.RubyObject{
    public static org.jruby.runtime.builtin.IRubyObject __allocate__(org.jruby.Ruby, org.jruby.RubyClass);
    public MyClass();
    public java.lang.Object foo();
    static {};
}