在JComboBox中更改滚动条的大小

import javax.swing.*;
import javax.swing.plaf.basic.BasicComboBoxUI;
import java.awt.*;

public class CustomComboBoxUI extends BasicComboBoxUI {
    @Override
    protected ComboPopup createPopup() {
        // 创建弹出窗口
        BasicComboPopup popup = (BasicComboPopup) super.createPopup();
        
        // 获取滚动条
        JScrollPane scrollPane = (JScrollPane) popup.getComponent(0);
        JScrollBar scrollBar = scrollPane.getVerticalScrollBar();
        
        // 设置滚动条大小
        scrollBar.setPreferredSize(new Dimension(20, 100));
        
        return popup;
    }
    
    public static void main(String[] args) {
        // 创建JComboBox
        JComboBox<String> comboBox = new JComboBox<>();
        comboBox.addItem("Option 1");
        comboBox.addItem("Option 2");
        comboBox.addItem("Option 3");
        
        // 设置自定义UI
        comboBox.setUI(new CustomComboBoxUI());
        
        // 显示JComboBox
        JFrame frame = new JFrame();
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.getContentPane().add(comboBox);
        frame.pack();
        frame.setVisible(true);
    }
}