Thread and Static

[vincent2001@gmail.com]

Hi Everyone,

This is my first post,thanks in advance for your help

I was reading an example which explains the use of SwingUtilities, then I simply come up with two ideas which proved to be wrong...Can you help give me some explaination,thanks!

The code is very simple..Creat a jframe ,inside it,there is jlabel, after one second the jlabel's text is changed;

What confuses me is why declare "static test1 ssp;"

import javax.swing.*;

import java.util.*;
import java.util.concurrent.TimeUnit;

public class test1 extends JFrame{

JLabel label;
public test1(){
super("hi");
label=new JLabel("label");
add(label);
setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
setSize(300,100);
setVisible(true);

}
//look at the following line
static test1 ssp;
public static void main(String[] args) throws Exception{
SwingUtilities.invokeLater(new Runnable(){
public void run(){ssp=new test1();}}
);
TimeUnit.SECONDS.sleep(1);
SwingUtilities.invokeLater(new Runnable(){


public void run(){
ssp.label.setText("hi"); }
}
);

}
}

The above Code is the example..runs correctly.
then I change the code like this ( no static test1 ssp any more)

public static void main(String[] args) throws Exception{
SwingUtilities.invokeLater(new Runnable(){
public void run(){test1 ssp=new test1();}}
);
TimeUnit.SECONDS.sleep(1);
SwingUtilities.invokeLater(new Runnable(){
public void run(){
ssp.label.setText("hi"); }
}
);

}
}
Now there is error message popping up saying that"SSP can't be resolved"

I don't get this...ssp as object of test1 has been created in the first SwingUtilities 1 seconde before the seconde SwingUtilites..then why it can't resolve SSP? is this because of two threads?or....


This way


public static void main(String[] args) throws Exception{
SwingUtilities.invokeLater(new Runnable(){
public void run(){
test1 ssp=new test1();
TimeUnit.SECONDS.sleep(1);
ssp.label.setText("hi");} }
);


}


then there is promting "unhandled exception for TimeUnit...."

[Norm]

ublic void run(){test1 ssp=new test1();}}
);

You define ssp as a variable that is local to the run method. NO code outside of the run method can see ssp.

has been created in the first SwingUtilities 1 seconde before the seconde

It looks like you are confusing compile time with run time. I assume that the error occurs during compilation. The 1 second before would be at runtime.

When you get errors, please copy and paste them here. Don't edit them.

[vincent2001@gmail.com]

Thanks norm,

you got the point! I confuse two things
1) Compile time and run time
2) Local variable inside Run() ...

I thought everything inside Main() is in one scope....;(

and thanks for telling me that I should copy and paste the error message here.That was my first post..