请问下面哪里错了？

博北A209 2015-05-03 01:12:06



package com.machine.study;





import java.awt.BorderLayout;

import java.awt.Container;

import java.awt.Font;

import java.awt.TextArea;

import java.awt.Toolkit;

import java.awt.event.ActionEvent;

import java.awt.event.ActionListener;

import java.awt.event.InputEvent;

import java.awt.event.KeyEvent;

import java.awt.event.WindowAdapter;

import java.awt.event.WindowEvent;



import javax.swing.JFrame;

import javax.swing.JMenu;

import javax.swing.JMenuBar;

import javax.swing.JMenuItem;

import javax.swing.JPopupMenu;

import javax.swing.JScrollPane;

import javax.swing.JTextArea;

import javax.swing.KeyStroke;

import javax.swing.ScrollPaneConstants;



public  class StudyTest extends JFrame{    //继承Jframe父类

	private JMenu fileMenu;

	private JMenuItem menuOpenTrain;

	private JMenuItem menuOpenPredict;

	

	private JMenu runMenu;

	private JMenuItem firstMenu;

	private JMenuItem secondMenu;

	private JMenuItem thirdMenu;

	private JMenuItem fourthMenu;

	

	private JMenu aboutMenu;

	private JMenuItem introduceMenu;

	private JMenuItem hearGetMenu;

	

	private JTextArea showArea;

	

	private JPopupMenu popUpMenu;

	

	public StudyTest(){

		super("机器学习与测试");

		int w = (Toolkit.getDefaultToolkit().getScreenSize().width - WIDTH) /4;

		int h = (Toolkit.getDefaultToolkit().getScreenSize().height - HEIGHT) /5;

		setLocation(w, h);//使界面在屏幕中间显示

		setUpUIComponent();   //界面设计函数

		setUpEventListener();   //事件处理

		setVisible(true);   //显示窗口

	}  

	

	private void setUpUIComponent() {  //界面设计函数

		setSize(640,480);//设计主界面的大小

		//菜单栏

		JMenuBar menuBar =new JMenuBar();

		//设置文件菜单

		JMenu fileMenu =new JMenu("文件");	

		JMenuItem menuOpenTrain =new JMenuItem("载入训练集");//打开训练集

		//快捷键设置

		menuOpenTrain.setAccelerator(KeyStroke.getKeyStroke(KeyEvent.VK_Z,InputEvent.CTRL_MASK));

		JMenuItem menuOpenPredict =new JMenuItem("载入测试集");//打开测试集

		//设置快捷键

		menuOpenPredict.setAccelerator(KeyStroke.getKeyStroke(KeyEvent.VK_X,InputEvent.CTRL_MASK));

		fileMenu.add(menuOpenTrain);  //显示在主界面上

		fileMenu.addSeparator();      //分隔线

		fileMenu.add(menuOpenPredict);  //显示在主界面上

		fileMenu.addSeparator();      //分隔线

		//设置执行菜单

		JMenu runMenu =new JMenu("执行");

		JMenuItem firstMenu =new JMenuItem("采用线性核函数");//采用线性核函数

		JMenuItem secondMenu =new JMenuItem("采用多项式核函数");//采用多项式核函数

		JMenuItem thirdMenu =new JMenuItem("采用RBF核函数");//采用RBF核函数

		JMenuItem fourthMenu =new JMenuItem("十折交叉验证");//打开训练集

		runMenu.add(firstMenu);  

		runMenu.addSeparator();

		runMenu.add(secondMenu);  

		runMenu.addSeparator();

		runMenu.add(thirdMenu);  

		runMenu.addSeparator();

		runMenu.add(fourthMenu);   

		runMenu.addSeparator();

		//设置关于菜单

		JMenu aboutMenu=new JMenu("关于");

		JMenuItem introduceMenu =new JMenuItem("关于程序");

		JMenuItem hearGetMenu =new JMenuItem("关于设计心得");

		aboutMenu.add(introduceMenu);

		aboutMenu.add(hearGetMenu);

		menuBar.add(fileMenu);//显示文件菜单

		menuBar.add(runMenu);//显示执行菜单

		menuBar.add(aboutMenu);//显示关于菜单

		setJMenuBar(menuBar);//设置菜单栏

		//结果显示区域设置

		JTextArea showArea =new JTextArea();//结果显示区域

		showArea.setFont(new Font("宋体",Font.PLAIN,16));//设置显示文字的书体

		showArea.setLineWrap(true); //设置自动换行

		//设置滚动条，已设置自动化换行就没有水平滚动条

		JScrollPane panel =new JScrollPane(showArea,ScrollPaneConstants.VERTICAL_SCROLLBAR_AS_NEEDED,ScrollPaneConstants.HORIZONTAL_SCROLLBAR_NEVER);

		Container contentPane =getContentPane();//在JFrame中获取ContentPane

		contentPane.add(panel, BorderLayout.CENTER);

		popUpMenu =runMenu.getPopupMenu();

	}

	

	private void setUpEventListener() {  //事件处理函数

		setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);//单击X后关闭界面

		//菜单---载入训练集

		menuOpenTrain.addActionListener(

				new ActionListener() {     //事件监听器

					public void actionPerformed(ActionEvent e) {

						openTrainFile();    //载入训练集函数 ------此处写上事件处理函数

					}

				}

		);

	}

	protected void openTrainFile() {   //载入训练集函数

		// TODO Auto-generated method stub

		

	}



	public static void main(String[] args) throws Exception{

		new StudyTest();

	}

}

程序错误为：
Exception in thread "main" java.lang.NullPointerException
at com.machine.study.StudyTest.setUpEventListener(StudyTest.java:109)
at com.machine.study.StudyTest.<init>(StudyTest.java:51)
at com.machine.study.StudyTest.main(StudyTest.java:123)

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