Code from swing tutorial

Question

hi this is code from sun's swing tutorial (http://java.sun.com/docs/books/tutorial/uiswing/learn/example1.html )
import javax.swing.*;       
public class HelloWorldSwing
private static void createAndShowGUI()    // why it is private ??
        JFrame.setDefaultLookAndFeelDecorated(true);
        JFrame frame = new JFrame("HelloWorldSwing");
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        JLabel label = new JLabel("Hello World");
        frame.getContentPane().add(label);
        frame.pack();
        frame.setVisible(true);
   public static void main(String[] args) {
             javax.swing.SwingUtilities.invokeLater(new Runnable()  // what does this snippet doing ?
            public void run()
                createAndShowGUI();
}i have question on this code. i have put my question in the comment . in the tutorial they are advising to " Be thread safe ...what it means ?
can anybody explain my questions ( commentation + bold letter) ?
thanks

Answer 1

i have seen swing codes which dont use threads
like above . does it mean they are not safe ?
what do you mean by safe ? ...does it mean program
can crash at any time if i dont include that
snippet ? will you be explicit in a simpler way.It is extremely unlikely that doing the following is unsafe:
//in main thread:
frame.pack();
frame.setVisible(true); //unsafe?But there's no guarantee! And by unsafe, the authors mean that undefined behavior can result --
your GUI could do anything it wanted! That being said, it's extremely unlikely that anything bad
would result in this example -- it's too simple. I do remember someone posting once that they
finally tracked an intermittent bug in their app to just this!
What I do, if I'm being safe/paranoid is call a utility method I've written, instead of calling setVisible
in the above code:
public static void postVisible(final JFrame f, final boolean state) {
    Runnable r = new Runnable() {
        public void run() {
            f.setVisible(state);
    SwingUtilities.invokeLater(r);
}Problem solved!
>
second question was why the method was private
static......why not public static ?(if you really
want to make it static !!)1. Since they never instantiate HelloWorldSwing, the method had better be static.
2. Methods should have the most restrictive scope possible. Since this is the "main" class
that launches its own GUI, no other class needs to see createAndShowGUI, so it is private.