Thread: GUI problem

Hello everyone

I have this code and whenever i run it i get this error message. I tried to fix it but i dont know what is wrong with it.

HTML Code:

package D;

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

public class D extends JFrame implements ActionListener {

    JButton Exit, Name;
    String fn,ln;
    
    public D() {
    
        this.setSize(400,300);
        this.setTitle("Celsius and Fahrenheit conversion");
        this.setVisible(true);
        this.setLocationRelativeTo(null);
        this.setLayout(new FlowLayout());
        
        Container content = getContentPane();
        
        Exit = new JButton("Close Program");
        Exit.setActionCommand("Exit");
        
        
        Name = new JButton("Enter Name");
        Name.setActionCommand("Name");
        
        Exit.addActionListener(this);
        Name.addActionListener(this);
        
        content.add(Exit, BorderLayout.NORTH);
        content.add(Name, BorderLayout.WEST);
    }
    
    public void Actions(ActionEvent Action) {
        if(Action.getActionCommand().contains("Exit")) {
            System.exit(0);
        }
        
        if(Action.getActionCommand().equals("Name")) {
            
            fn = JOptionPane.showInputDialog("Enter First Name: ");
            ln = JOptionPane.showInputDialog("Enter Last Name: ");
            
            JOptionPane.showMessageDialog(null, "Hello " + fn + " " + ln);
        }
    }
    public static void main(String[] args) {
        D();
    }
}

Error Message:-

HTML Code:

run:
java.lang.NoClassDefFoundError: d/D (wrong name: D/D)
	at java.lang.ClassLoader.defineClass1(Native Method)
	at java.lang.ClassLoader.defineClass(ClassLoader.java:791)
	at java.security.SecureClassLoader.defineClass(SecureClassLoader.java:142)
	at java.net.URLClassLoader.defineClass(URLClassLoader.java:449)
	at java.net.URLClassLoader.access$100(URLClassLoader.java:71)
	at java.net.URLClassLoader$1.run(URLClassLoader.java:361)
	at java.net.URLClassLoader$1.run(URLClassLoader.java:355)
	at java.security.AccessController.doPrivileged(Native Method)
	at java.net.URLClassLoader.findClass(URLClassLoader.java:354)
	at java.lang.ClassLoader.loadClass(ClassLoader.java:423)
	at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:308)
	at java.lang.ClassLoader.loadClass(ClassLoader.java:356)
	at sun.launcher.LauncherHelper.checkAndLoadMain(LauncherHelper.java:472)
Exception in thread "main" Java Result: 1
BUILD SUCCESSFUL (total time: 1 second)