java需要帮助来修复ComboBox编程错误

Question

我其实是个新手，只是自学而已。我真的很想学习如何正确使用JComboBox。我创建了一个简单的程序，但我花了很长时间来修复它

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

您忘记了变量的名称

而不是

JComboBox = new JComboBox();

试试看

JComboBox j = new JComboBox();
          ^

但是，正如iTech所建议的，您可能想要创建一个类的实例

new SampleButtonKo();

Answer 2

代码中明显很少有错误，您需要将constructor命名为与您的类完全相同的名称，并且没有返回类型。其次，在main中，应该创建类的实例而不是the JComboBox

public class SampleButtonKo{
  JComboBox combo;

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

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