Path: csiph.com!usenet.pasdenom.info!gegeweb.org!eternal-september.org!feeder.eternal-september.org!mx04.eternal-september.org!.POSTED!not-for-mail From: bilsch Newsgroups: comp.lang.java.programmer Subject: Re: I need a different approach - suggestions please Date: Tue, 26 Jun 2012 13:24:09 -0700 Organization: A noiseless patient Spider Lines: 66 Message-ID: References: Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Injection-Date: Tue, 26 Jun 2012 20:24:10 +0000 (UTC) Injection-Info: mx04.eternal-september.org; posting-host="VpQo9AeuZ2WQvbzkl6vgHQ"; logging-data="26565"; mail-complaints-to="abuse@eternal-september.org"; posting-account="U2FsdGVkX1+XTVcXgsRz3bqrMmTeZUoP" User-Agent: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:12.0) Gecko/20120428 Thunderbird/12.0.1 In-Reply-To: Cancel-Lock: sha1:AcSWUuV0fwrf6CAubq1Z389c0HE= Xref: csiph.com comp.lang.java.programmer:15607 On 6/25/2012 6:36 PM, Lew wrote: > bilsch wrote: >> markspace wrote: >>> bilsch wrote: >>>> I'm trying to make a program that works like the calculator in Windows >>>> Accessories - all input is from button clicks. ... >>>> Everytime the method is called the string is reinitialized >>>> with the result that my sequence of digits is only ever one digit long. >>>> My plan would work if I could initialize the string outside the method, >>>> however variable scope in Java doesn't allow it. >>> >>> First, good job on making a very reasonable SSCCE. >>> >>> Second, the trick to Java's scoping rules is to change the rules! >>> >>> Move the string strng1 from inside the actionPerformed to outside, right >>> below the CalcGUIQ1 gui; line. Now Java's scoping rules help you rather >>> than hinder you. >>> >>> BTW, this looks like a homework problem, and it looks like you've been >>> getting help on it. Some if it is a bit sophisticated for someone who >>> doesn't understand scoping. Please try to talk to your instructor or a >>> TA, they need to understand when you're having problems with your lessons. >>> >> Thanks for the help. I could swear I tried that first but got error >> messages about static and non-static conflict problem. i will be taking >> Java in fall quarter. Right now I'm working from "Learn Java in 24 >> Hours" I thought up the calculator project myself. Thanks again. > > There are a few mistakes in your code. > > You don't need to call 'super()' in the constructor explicitly. > That's what happens by default anyway. > > You called the constructor directly from the 'main()' routine. That means > you called it from the primary thread of the program. You don't know this > yet, probably, unless you've already studied concurrency in Java a little bit. > > The problem is that the GUI won't work right if you do that. You have to > move GUI actions onto the "Event Dispatch Thread" (EDT), a background > thread that the system creates to handle all GUI actions. > > Also, you start all the action from the constructor. That's bad. As its name > implies, a constructor's purpose is to _construct_ an object, not run its logic. > Run the logic after construction completes and the instance is no longer in a > partially-built state. > > And make your indentation consistent with the Java coding conventions (available > on line). > > So all together, you'd do something like: > > public static void main(String[] arguments) { > java.awt.EventQueue.invokeAndWait( new Runnable() { > @Override public void run() { > CalcGUIQ1 calculator = new CalcGUIQ1(); > calculator.setVisible(true); > } > }); > } Many things are because I mimic what I see in other programs. Your advise is appreciated and noted. I know my indentation is wrong - it is something I'll have to work on. I hope I can finish this project without understanding threads because I read about them and I don't see that they apply here. I don't really understand them.