Java实现简易记事本程序

import java.awt.*;
import java.awt.event.*;
import java.io.*;

import javax.swing.*;

public class MyNotepad implements ActionListener{
private JFrame frame=new JFrame("新记事本");
private JTextArea jta=new JTextArea();
private String result="";
private boolean flag=true;
private File f;
private JButton jb=new JButton("开始");
private JTextField jtf=new JTextField(15);
private JTextField jt=new JTextField(15);
private JButton jbt=new JButton("替换为");
private JButton jba=new JButton("全部替换");
private Icon ic=new ImageIcon("D:\\java课堂笔记\\GUI\\11.gif");
private String value;
private int start=0;
private JFrame jf=new JFrame("查找");
private JFrame jfc=new JFrame("替换");

@Override
public void actionPerformed(ActionEvent e) {
String comm=e.getActionCommand();
if("新建".equals(comm)){
if(!(frame.getTitle().equals("新记事本"))){
if(!flag){
write();

newNew();
}else{
JFileChooser jfc=new JFileChooser("D:\\java课堂笔记");
 int returnVal = jfc.showDialog(null,"保存为");
 if(returnVal == JFileChooser.APPROVE_OPTION) {//选择文件后再执行下面的语句，保证了程序的健壮性
            f=jfc.getSelectedFile();
            flag=false;
write();
    }
}
}else if(!(jta.getText().isEmpty())){
JFileChooser jfc=new JFileChooser("D:\\java课堂笔记");
 int returnVal = jfc.showDialog(null,"保存为");
 if(returnVal == JFileChooser.APPROVE_OPTION) {//选择文件后再执行下面的语句，保证了程序的健壮性
            f=jfc.getSelectedFile();
            flag=false;
write();
newNew();
    }
}else{
newNew();
}
}else if("打开".equals(comm)){
JFileChooser jfc=new JFileChooser("D:\\java课堂笔记");
jfc.setDialogType(JFileChooser.OPEN_DIALOG);
 int returnVal = jfc.showOpenDialog(null);
 if(returnVal == JFileChooser.APPROVE_OPTION) {//选择文件后再执行下面的语句，保证了程序的健壮性
f=jfc.getSelectedFile();
frame.setTitle(f.getName());
result=read();