java file (IO) programming--Simple notepad development

1 public class NotePad extends JFrame implements ActionListener{
Two
3 / / define the required components
4 jtextarea JTA = null; / / multiline text box
Five
6 jmenubar JMB = null; / / menu bar
7 JMenu jm1 = null; / / menu
8 jmuitem jmi1 = null, jmi2 = null; / / menu item
Nine
10     public static void main(String[] args) {
11         NotePad np=new NotePad();
Twelve
13}
Fourteen
15 public notepad() {/ / constructor
Sixteen
17 JTA = new jtextarea(); / / create JTA
18         jmb=new JMenuBar();
19 jm1 = new JMenu ("file");
20 jm1.setmnemonic ('f '); / / set mnemonic
Twenty-one
22 jmi1 = new jmenuitem ("open", new imageicon ("imag_3. JPG");
23 jmi1. Addactionlistener (this); / / register to listen
24         jmi1.setActionCommand("open");
Twenty-five
26 jmi2 = new jmenuitem ("save");
27         jmi2.addActionListener(this);
28         jmi2.setActionCommand("save");
Twenty-nine
30 this. Setjmenubar (JMB); / / add
Thirty-one
32 JMB. Add (jm1); / / put the menu into the menu bar
Thirty-three
34 jm1. Add (jmi1); / / put item into menu
35         jm1.add(jmi2);
Thirty-six
37 this. Add (JTA); / / put it into JFrame
Thirty-eight
39         this.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
40         this.setSize(400,300);
41 this.settitle ("NOTEPAD");
42         this.setIconImage((new ImageIcon("imag_2.jpg")).getImage());
43         this.setVisible(true);
44}
Forty-five
46     @Override
47     public void actionPerformed(ActionEvent arg0) {
48 / / judge which menu is selected
49         if(arg0.getActionCommand().equals("open")){
Fifty
51 / / Jfilechooser, create a file selection component
52             JFileChooser jfc1=new JFileChooser();
53 jfc1.setdialogtitle ("please select File "); / / set the name
Fifty-four
55 jfc1.showopendialog (null); / / default
56 jfc1. Setvisible (true); / / display
Fifty-seven
58 / / get the full path of the file selected by the user
59             String filename=jfc1.getSelectedFile().getAbsolutePath();
Sixty
61             FileReader fr=null;
62             BufferedReader br=null;
Sixty-three
64             try {
65                 fr=new FileReader(filename);
66                 br=new BufferedReader(fr);
Sixty-seven
68 / / read the information from the file and display it to JTA
69                 String s="";
70                 String allCon="";
71 while ((s = br. Readline())! = null) {/ / loop to read the file. If s is not empty, it is not read
72                     allCon+=s+"\r\n";
73                 }
Seventy-four
75 JTA. Settext (allcon); / / place it in JTA
Seventy-six
77             } catch (Exception e) {
78                 e.printStackTrace();
79             }finally{
Eighty
81                 try {
82                     fr.close();
83                     br.close();
84                 } catch (Exception e) {
85                     e.printStackTrace();
86                 }
87             }
88         }else if(arg0.getActionCommand().equals("save")){
89 / / the save dialog box appears
90             JFileChooser jfc2=new JFileChooser();
91 jfc2.setdialogtitle ("save as "";
92 jfc2.showsavedialog (null); / / display by default
93             jfc2.setVisible(true);
Ninety-four
95 / / get where the user wants to save the file and the full path of the file
96             String filename2=jfc2.getSelectedFile().getAbsolutePath();
Ninety-seven
98 / / prepare to write to the specified file
99             FileWriter fw=null;
100             BufferedWriter bw=null;
One hundred and one
102             try {
103                 fw=new FileWriter(filename2);
104                 bw=new BufferedWriter(fw);
One hundred and five
106                 bw.write(this.jta.getText());
107             } catch (Exception e) {
108                 e.printStackTrace();
109             }finally{
110                 try {
111                     bw.close();
112                 } catch (IOException e) {
113                     e.printStackTrace();
114                 }
115             }
116         }
117}
118} 

The results are as follows:

Click the File button, click the Open menu item, select a text file, the effect is as follows:

When opened, the content is displayed as follows:

Modify the content slightly, save as a file named SSS, the effect is as follows:

java file (IO) programming--Simple notepad development