thufir@arrakis:~/sun_tutorial$ 
thufir@arrakis:~/sun_tutorial$ ruby compile.rb 
compile.rb:4: warning: parenthesize argument(s) for future version
thufir@arrakis:~/sun_tutorial$ 
thufir@arrakis:~/sun_tutorial$ cat compile.rb 
def compile
        puts "compiling..."

        system(javac HelloWorldApp.java)
end
thufir@arrakis:~/sun_tutorial$ 
thufir@arrakis:~/sun_tutorial$ javac HelloWorldApp.java 
thufir@arrakis:~/sun_tutorial$