Re: java:143: cannot find symbol -----Please help me

From: Andrew Thompson (SeeMySites_at_www.invalid)
Date: 05/26/04 

Date: Wed, 26 May 2004 08:41:14 GMT

On Wed, 26 May 2004 16:04:20 +0800, Danny wrote:

I have an answer for you, but first, some comments..

You need to have a close look over this
<http://www.physci.org/codes/sscce.jsp>

It explains how you might have represented this
problem in 91 lines, rather than 391

> import java.lang.*;

..no need to import this

> class MyFrame extends JFrame

Terrible name, it sounds like the 'I, me, mine..'
phase of toddlers a class name should tell basically
what it is, so, for instance..
'RetailServerFrame'

> {
> JFrame frame;
> JButton buttonStart;
> JButton buttonExit;
> String userInput;
> String serverName;
> String userName;
> String password;

These are 'class level' attributes, anything
in the class has access to them.

> public static void main(String args[])
> {
> MyFrame f = new MyFrame();
> }
>
> public MyFrame()
> {
> super("Window Title");
>
> JLabel labelSpace;
> JLabel labelTitle;
> JLabel labelServername;

Whereas this is a local variable declared within
the constructor, nothing outside the constructor
can access it.

> ....
> class ButtonListener implements ActionListener
> {
>
> public void actionPerformed(ActionEvent evt)
> {
> JButton source = (JButton)evt.getSource();
> serverName = textServername.getText();
> System.out.println(serverName);
> }
>
> }
> }

So by this stage, the textServerName label is
'out of scope', or 'not visible'.

Solution, declare it as a class level
attribute, and the code will compile. 

-- 
Andrew Thompson
http://www.PhySci.org/ Open-source software suite
http://www.PhySci.org/codes/ Web & IT Help
http://www.1point1C.org/ Science & Technology

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