Problemas: Swing e dificuldade em obter documentação

import javax.swing.*;

public class UmaPop {
	public static void main(String[] argumentin) {
		JOptionPane.showMessageDialog(null,"alert","alert",JOptionPane.ERROR_MESSAGE);
		JOptionPane.showMessageDialog(null,"alert","alert",0); 	
	}
}

/*
Descobri que "0" e "JOptioPane.ERROR_MESSAGE" são sinônimos, mas através do código de um amigo meu, e não através de documentação.

Veja link:
http://java.sun.com/j2se/1.5.0/docs/api/javax/swing/JOptionPane.html
*/

import org.eclipse.swt.widgets.Display;
import org.eclipse.swt.widgets.Shell;

public class HelloWorldSWT {

	/**
	 * @param args
	 */
	public static void main(String[] args) {
		// TODO Auto-generated method stub

		Display display = new Display();
		Shell shell = new Shell(display);
		shell.setText("Hello world!");
		shell.open();
		while (!shell.isDisposed()) {
			if (!display.readAndDispatch()) display.sleep();
		}
		
		display.dispose();
		

	}

}

import javax.swing.*;

package components;

/* TextDemo.java requires no other files. */

import java.awt.*;
import java.awt.event.*;
import javax.swing.*;

public class TextDemo extends JPanel implements ActionListener {
    protected JTextField textField;
    protected JTextArea textArea;
    private final static String newline = "\n";

    public TextDemo() {
        super(new GridBagLayout());

        textField = new JTextField(20);
        textField.addActionListener(this);

        textArea = new JTextArea(5, 20);
        textArea.setEditable(false);
        JScrollPane scrollPane = new JScrollPane(textArea,
                                       JScrollPane.VERTICAL_SCROLLBAR_ALWAYS,
                                       JScrollPane.HORIZONTAL_SCROLLBAR_ALWAYS);

        //Add Components to this panel.
        GridBagConstraints c = new GridBagConstraints();
        c.gridwidth = GridBagConstraints.REMAINDER;

        c.fill = GridBagConstraints.HORIZONTAL;
        add(textField, c);

        c.fill = GridBagConstraints.BOTH;
        c.weightx = 1.0;
        c.weighty = 1.0;
        add(scrollPane, c);
    }

    public void actionPerformed(ActionEvent evt) {
        String text = textField.getText();
        textArea.append(text + newline);
        textField.selectAll();

        //Make sure the new text is visible, even if there
        //was a selection in the text area.
        textArea.setCaretPosition(textArea.getDocument().getLength());
    }

    /**
     * Create the GUI and show it.  For thread safety,
     * this method should be invoked from the
     * event dispatch thread.
     */
    private static void createAndShowGUI() {
        //Create and set up the window.
        JFrame frame = new JFrame("TextDemo");
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

        //Add contents to the window.
        frame.add(new TextDemo());

        //Display the window.
        frame.pack();
        frame.setVisible(true);
    }

    public static void main(String[] args) {
        //Schedule a job for the event dispatch thread:
        //creating and showing this application's GUI.
        javax.swing.SwingUtilities.invokeLater(new Runnable() {
            public void run() {
                createAndShowGUI();
            }
        });
    }
}

C:\USR\CVV\BlueJ\Pro\Sun>javac TextDemo.java

C:\USR\CVV\BlueJ\Pro\Sun>java TextDemo
Exception in thread "main" java.lang.NoClassDefFoundError: TextDemo (wrong name:
 components/TextDemo)
        at java.lang.ClassLoader.defineClass1(Native Method)
        at java.lang.ClassLoader.defineClass(Unknown Source)
        at java.security.SecureClassLoader.defineClass(Unknown Source)
        at java.net.URLClassLoader.defineClass(Unknown Source)
        at java.net.URLClassLoader.access$000(Unknown Source)
        at java.net.URLClassLoader$1.run(Unknown Source)
        at java.security.AccessController.doPrivileged(Native Method)
        at java.net.URLClassLoader.findClass(Unknown Source)
        at java.lang.ClassLoader.loadClass(Unknown Source)
        at sun.misc.Launcher$AppClassLoader.loadClass(Unknown Source)
        at java.lang.ClassLoader.loadClass(Unknown Source)
        at java.lang.ClassLoader.loadClassInternal(Unknown Source)

(wrong name: components/TextDemo)

//package components;

//package components;

/* TextDemo.java requires no other files. */

import java.awt.*;
import java.awt.event.*;
import javax.swing.*;

public class TextDemo extends JPanel implements ActionListener {
    protected JTextField textField;
    protected JTextArea textArea;
    private final static String newline = "\n";

    public TextDemo() {
        super(new GridBagLayout());

        textField = new JTextField(20);
        textField.addActionListener(this);

        textArea = new JTextArea(5, 20);
        textArea.setEditable(false);
        JScrollPane scrollPane = new JScrollPane(textArea,
                                       JScrollPane.VERTICAL_SCROLLBAR_ALWAYS,
                                       JScrollPane.HORIZONTAL_SCROLLBAR_ALWAYS);

        //Add Components to this panel.
        GridBagConstraints c = new GridBagConstraints();
        c.gridwidth = GridBagConstraints.REMAINDER;

        c.fill = GridBagConstraints.HORIZONTAL;
        add(textField, c);

        c.fill = GridBagConstraints.BOTH;
        c.weightx = 1.0;
        c.weighty = 1.0;
        add(scrollPane, c);
    }

    public void actionPerformed(ActionEvent evt) {
        String text = textField.getText();
        textArea.append(text + newline);
        textField.selectAll();

        //Make sure the new text is visible, even if there
        //was a selection in the text area.
        textArea.setCaretPosition(textArea.getDocument().getLength());
    }

    /**
     * Create the GUI and show it.  For thread safety,
     * this method should be invoked from the
     * event dispatch thread.
     */
    private static void createAndShowGUI() {
        //Create and set up the window.
        JFrame frame = new JFrame("TextDemo");
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

        //Add contents to the window.
        frame.add(new TextDemo());

        //Display the window.
        frame.pack();
        frame.setVisible(true);
    }

    public static void main(String[] args) {
        //Schedule a job for the event dispatch thread:
        //creating and showing this application's GUI.
        javax.swing.SwingUtilities.invokeLater(new Runnable() {
            public void run() {
                createAndShowGUI();
            }
        });
    }
}