怎么使textarea怎么实现combobox里面的item事件

package com.great.nf1108.demo;

import java.awt.*;

import java.awt.event.*;

import javax.swing.*;

public class LayoutExciseFrame extends JFrame {

JLabel labFace = new JLabel("字体");
JLabel labSize = new JLabel("大小");
JComboBox comboBoxFace = new JComboBox();
JComboBox comboBoxSize = new JComboBox();
JRadioButton checkBoxBold = new JRadioButton("粗体");
JRadioButton checkBoxItalic = new JRadioButton("斜体");
JTextArea txtArea = new JTextArea("这里是设置字体的预览区,示例文字");
ButtonGroup spRadioButton = new ButtonGroup();

public LayoutExciseFrame() {

    setTitle("设置字体");
    setSize(500, 400);

    initComponent();

    initLayout();

    setMenu();
    setVisible(true);
    setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

}

/**
 * 初始化布局
 */
private void initLayout() {
    JPanel panelLeft = new JPanel();// 左侧布局面板
    JPanel panelTop = new JPanel();// 顶部布局面板
    JPanel panelBottom = new JPanel();// 底部布局面板
    JPanel panelFace = new JPanel();// 放置字体设置相关控件的 面板
    JPanel panelSize = new JPanel();// 放置大小设置相关控件的 面板

    panelFace.setLayout(new FlowLayout(FlowLayout.LEFT));
    panelFace.add(labFace);

    spRadioButton.add(checkBoxBold);
    spRadioButton.add(checkBoxItalic);
    panelFace.add(comboBoxFace);

    panelSize.setLayout(new FlowLayout(FlowLayout.LEFT));
    panelSize.add(labSize);
    panelSize.add(comboBoxSize);

    panelTop.setLayout(new GridLayout(2, 1));
    panelTop.add(panelFace);
    panelTop.add(panelSize);

    panelBottom.setLayout(new GridLayout(6, 1));
    panelBottom.add(new JPanel());
    panelBottom.add(new JPanel());
    JPanel panelBold = new JPanel();
    panelBold.add(checkBoxBold);
    JPanel panelItatic = new JPanel();
    panelItatic.add(checkBoxItalic);
    panelBottom.add(panelBold);
    panelBottom.add(panelItatic);
    panelBottom.add(new JPanel());
    panelBottom.add(new JPanel());

    panelLeft.setLayout(new BorderLayout());
    panelLeft.add(panelTop, BorderLayout.NORTH);
    panelLeft.add(panelBottom);

    add(panelLeft, BorderLayout.WEST);
    add(txtArea);
}

/**
 * 初始化组件
 */
public void initComponent() {

    comboBoxFace.addItem("宋体");
    comboBoxFace.addItem("楷体-GB2312");
    comboBoxSize.addItem(12);
    comboBoxSize.addItem(14);
    comboBoxSize.addItem(24);
}

/**
 * 设置菜单
 */
private void setMenu() {
    MenuBar menuBar = new MenuBar();

    Menu menuColor = new Menu("字体颜色");

    MenuItem menuItemRed = new MenuItem("红色");
    MenuItem menuItemBlue = new MenuItem("蓝色");
    MenuItem menuItemGreen = new MenuItem("绿色");

    // 把菜单项放入菜单
    menuColor.add(menuItemRed);
    menuColor.add(menuItemGreen);
    menuColor.add(menuItemBlue);

    // 将菜单加入到菜单条中
    menuBar.add(menuColor);

    setMenuBar(menuBar);// 设置菜单条到当前窗口中

}

}