Need help to fix ComboBox programming error

Question

I'm a kinda newbie actually and just self-studying. I really want to learn how to use JComboBox properly. I have created a simple program but it took me forever to fix it.

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

public class SampleButtonKo {
    JComboBox combo;

    public void ComboBox1() {
        String course[] = {
            "PM1", "PM2", "PM3", "PM4"
        };
        JFrame frame = new JFrame("Mang Inasal Ordering System");
        JPanel panel = new JPanel();
        combo = new JComboBox(course);
        combo.setBackground(Color.gray);
        combo.setForeground(Color.red);
        panel.add(combo);
        frame.add(panel);

        combo.addItemListener(new ItemListener() {
            public void itemStateChanged(ItemEvent ie) {
                String str = (String) combo.getSelectedItem();
                System.out.print("You have chosen " + str);
            }
        });
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.setSize(400, 400);
        frame.setVisible(true);
    }

    public static void main(String[] args) {
        JComboBox = new JComboBox();
    }
}

Answer 1

There are obvious few errors in your code, you need to have the constructor named exactly as your class with no return type. Second, in your main you should create an instance of your class not the JComboBox

public class SampleButtonKo{
  JComboBox combo;

  public SampleButtonKo(){
     // Copy your code from "ComboBox1" here
  }

public static void main(String[] args) {
   new SampleButtonKo();
  }
}

Answer 2

You forgot a name for the variable

Instead of

JComboBox = new JComboBox();

try

JComboBox j = new JComboBox();
          ^

But perhaps, as iTech suggests, you want to create an instance of your class.

new SampleButtonKo();