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The main method is the entry point for a program in Java and if it isn't there it will get mad at you. Create the main method and then use the writeoutput method inside of it.

The closest error message I can get, using Eclipse, is "Void methods cannot return a value" but so long as you didn't change public String bottle(int bottle) to public void bottle(int bottle) I am...

I think posting the exact error message may shed some light on what the root cause is. So, if you haven't figured out this problem please post said message.