Very newbie trying to run form program
I am just starting to learn Java. I want to run the program listed below which is supposed to display a form (or a frame). It comipiles, I think, (javac TopLevelDemo.java) but when I try to run it with java TopLevelDemo I get a bunch of messages.
Exception in thread "main" java.lang.NoClassDefFoundError: TopLevelDemo <wrong name: components/TopLevelDemo>
at Java.Lang.ClassLoader
and the messages continue. Is this the correct way to run a program that makes a form? What am I doing wrong.
This is the code. I have omitted some comments.
Code:
package components;
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
/* TopLevelDemo.java requires no other files. */
public class TopLevelDemo {
/**
* Create the GUI and show it. For thread safety,
* this method should be invoked from the
* event-dispatching thread.
*/
private static void createAndShowGUI() {
//Create and set up the window.
JFrame frame = new JFrame("TopLevelDemo");
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
//Create the menu bar. Make it have a green background.
JMenuBar greenMenuBar = new JMenuBar();
greenMenuBar.setOpaque(true);
greenMenuBar.setBackground(new Color(154, 165, 127));
greenMenuBar.setPreferredSize(new Dimension(200, 20));
//Create a yellow label to put in the content pane.
JLabel yellowLabel = new JLabel();
yellowLabel.setOpaque(true);
yellowLabel.setBackground(new Color(248, 213, 131));
yellowLabel.setPreferredSize(new Dimension(200, 180));
//Set the menu bar and add the label to the content pane.
frame.setJMenuBar(greenMenuBar);
frame.getContentPane().add(yellowLabel, BorderLayout.CENTER);
//Display the window.
frame.pack();
frame.setVisible(true);
}
public static void main(String[] args) {
//Schedule a job for the event-dispatching thread:
//creating and showing this application's GUI.
javax.swing.SwingUtilities.invokeLater(new Runnable() {
public void run() {
createAndShowGUI();
}
});
}
}
