import java.io.*; import java.awt.*; import java.awt.event.*; import javax.swing.*; /** * This program lets the user edit short text files in a window. When a * file is being edited, the name of the file is displayed in the window's * title bar. A "File" menu provides the following commands: * * New -- Clears all text from the window. * Open -- Let's the user select a file and loads up to 100 * lines of text form that file into the window. The * previous contents of the window are lost. * Save -- Let's the user specify an output file and saves * the contents of the window in that file. * Quit -- Closes the window and ends the program. * * This very simple program is not meant for serious text editing. In * particular, a limit of 10000 characters is put on the size of the * files that it can read. */ public class TrivialEdit extends JFrame { /** * The main program just opens a window belonging to this TrivialEdit class. * Then the window takes care of itself until the program is ended with the * Quit command or when the user closes the window. */ public static void main(String[] args) { JFrame window = new TrivialEdit(); window.setVisible(true); } private JTextArea text; // Holds the text that is displayed in the window. private JFileChooser fileDialog; // File dialog for use in doOpen() an doSave(). private File editFile; // The file, if any that is currently being edited. /** * Create a TrivialEdit window, with a JTextArea where the user can * edit some text and with a menu bar. */ public TrivialEdit() { super("TrivialEdit: Untitled"); // Specifies title of the window. setJMenuBar( makeMenus() ); text = new JTextArea(25,50); text.setMargin( new Insets(3,5,0,0) ); // Some space around the text. JScrollPane scroller = new JScrollPane(text); setContentPane(scroller); setDefaultCloseOperation(EXIT_ON_CLOSE); pack(); setLocation(50,50); } /** * Create and return a menu bar containing a single menu, the * File menu. This menu contains four commands, New, Open, Save, * and Quit. */ private JMenuBar makeMenus() { ActionListener listener = new ActionListener() { // An object that will serve as listener for menu items. public void actionPerformed(ActionEvent evt) { // This will be called when the user makes a selection // from the File menu. This routine just checks // which command was selected and calls another // routine to carry out the command. String cmd = evt.getActionCommand(); if (cmd.equals("New")) doNew(); else if (cmd.equals("Open...")) doOpen(); else if (cmd.equals("Save...")) doSave(); else if (cmd.equals("Quit")) doQuit(); } }; JMenu fileMenu = new JMenu("File"); JMenuItem newCmd = new JMenuItem("New"); newCmd.addActionListener(listener); fileMenu.add(newCmd); JMenuItem openCmd = new JMenuItem("Open..."); openCmd.addActionListener(listener); fileMenu.add(openCmd); JMenuItem saveCmd = new JMenuItem("Save..."); saveCmd.addActionListener(listener); fileMenu.add(saveCmd); fileMenu.addSeparator(); JMenuItem quitCmd = new JMenuItem("Quit"); quitCmd.addActionListener(listener); fileMenu.add(quitCmd); JMenuBar bar = new JMenuBar(); bar.add(fileMenu); return bar; } // end makeMenus() /** * Carry out the "New" command from the File menu by clearing all * the text from the JTextArea. Also sets the title bar of the * window to read "TrivialEdit: Untitled". */ private void doNew() { text.setText(""); editFile = null; setTitle("TrivialEdit: Untitled"); } /** * Carry out the Save command by letting the user specify an output file * and writing the text from the JTextArea to that file. */ private void doSave() { if (fileDialog == null) fileDialog = new JFileChooser(); File selectedFile; //Initially selected file name in the dialog. if (editFile == null) selectedFile = new File("filename.txt"); else selectedFile = new File(editFile.getName()); fileDialog.setSelectedFile(selectedFile); fileDialog.setDialogTitle("Select File to be Saved"); int option = fileDialog.showSaveDialog(this); if (option != JFileChooser.APPROVE_OPTION) return; // User canceled or clicked the dialog's close box. selectedFile = fileDialog.getSelectedFile(); if (selectedFile.exists()) { // Ask the user whether to replace the file. int response = JOptionPane.showConfirmDialog( this, "The file \"" + selectedFile.getName() + "\" already exists.\nDo you want to replace it?", "Confirm Save", JOptionPane.YES_NO_OPTION, JOptionPane.WARNING_MESSAGE ); if (response != JOptionPane.YES_OPTION) return; // User does not want to replace the file. } PrintWriter out; try { FileWriter stream = new FileWriter(selectedFile); out = new PrintWriter( stream ); } catch (Exception e) { JOptionPane.showMessageDialog(this, "Sorry, but an error occurred while trying to open the file:\n" + e); return; } try { out.print(text.getText()); // Write text from the TextArea to the file. out.close(); if (out.checkError()) // (need to check for errors in PrintWriter) throw new IOException("Error check failed."); editFile = selectedFile; setTitle("TrivialEdit: " + editFile.getName()); } catch (Exception e) { JOptionPane.showMessageDialog(this, "Sorry, but an error occurred while trying to write the text:\n" + e); } } /** * Carry out the Open command by letting the user specify a file to be opened * and reading up to 10000 characters from that file. If the file is read * successfully and is not too long, then the text from the file replaces the * text in the JTextArea. */ public void doOpen() { if (fileDialog == null) fileDialog = new JFileChooser(); fileDialog.setDialogTitle("Select File to be Opened"); fileDialog.setSelectedFile(null); // No file is initially selected. int option = fileDialog.showOpenDialog(this); if (option != JFileChooser.APPROVE_OPTION) return; // User canceled or clicked the dialog's close box. File selectedFile = fileDialog.getSelectedFile(); BufferedReader in; try { FileReader stream = new FileReader(selectedFile); in = new BufferedReader( stream ); } catch (Exception e) { JOptionPane.showMessageDialog(this, "Sorry, but an error occurred while trying to open the file:\n" + e); return; } try { StringBuffer input = new StringBuffer(); while (true) { String lineFromFile = in.readLine(); if (lineFromFile == null) break; // End-of-file has been reached. input.append(lineFromFile); input.append('\n'); if (input.length() > 10000) throw new IOException("Input file is too large for this program."); } in.close(); text.setText(input.toString()); editFile = selectedFile; setTitle("TrivialEdit: " + editFile.getName()); } catch (Exception e) { JOptionPane.showMessageDialog(this, "Sorry, but an error occurred while trying to read the data:\n" + e); } } /** * Carry out the Quit command by exiting the program. */ private void doQuit() { System.exit(0); } } // end class TrivialEdit