基本的GUI基礎和IO基礎
核心程式碼

JFileChooser jfc = new JFileChooser();
jfc.setDialogTitle("另存為...");
// jfc.showOpenDialog(null); // 顯示開啟檔案對話方塊
jfc.showSaveDialog(null); // 顯示儲存檔案對話方塊
jfc.setVisible(true);

String filename = jfc.getSelectedFile().getAbsolutePath(); // 獲取選擇的檔案的絕對路徑

1 開啟檔案
2 儲存檔案
3 檔案選擇對話方塊

public
 
 class Base extends JFrame implements ActionListener{

private static final long serialVersionUID = -1131829311416485951L;


JTextArea jta = null;
JMenuBar jmb = null;
JMenu jm1 = null;
JMenuItem jmi1 = null, jmi2 = null;

public Base() {
    jta = new JTextArea();

    jmb = new JMenuBar();
    jm1 = new
 
 JMenu("檔案");
    jm1.setMnemonic('F');

    jmi1 = new JMenuItem("開啟");
    jmi2 = new JMenuItem("儲存");

    jmi1.addActionListener(this);
    jmi1.setActionCommand("open");
    jmi2.addActionListener(this);
    jmi2.setActionCommand("save");

    this.setJMenuBar(jmb);

    jmb.add(jm1);
    jm1.add(jmi1);
    jm1.addSeparator();
    jm1.add(jmi2);

    this
 
.add(jta);
    this.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    this.setSize(400, 300);
    this.setVisible(true);
}

//------------------------------------------------------
public void actionPerformed(ActionEvent e) {

        if(e.getActionCommand().equals("open")) {
            // 檔案選擇視窗
            JFileChooser jfc1 = new JFileChooser();
            jfc1.setDialogTitle("請選擇檔案...");

            jfc1.showOpenDialog(null);
            jfc1.setVisible(true);
            // 得到使用者選擇的檔案路徑
            String filename = jfc1.getSelectedFile().getAbsolutePath();

//          System.out.println(filename);
            BufferedReader br = null;
            try {
                br = new BufferedReader(new FileReader(filename));

                String s = "";
                String allCon = "";
                while((s=br.readLine())!=null) {
                    allCon+=s+"\r\n";
                }
                jta.setText(allCon);
            } catch (Exception e1) {
                e1.printStackTrace();
            } finally {
                try {
                    br.close();
                } catch (IOException e1) {
                    e1.printStackTrace();
                }
            }


        } else if(e.getActionCommand().equals("save")) {
            JFileChooser jfc2 = new JFileChooser();
            jfc2.setDialogTitle("另存為...");
            jfc2.showSaveDialog(null);
            jfc2.setVisible(true);

            String filename = jfc2.getSelectedFile().getAbsolutePath();

            BufferedWriter bw = null;

            try {
                bw = new BufferedWriter(new FileWriter(filename));

                bw.write(this.jta.getText());

            } catch (IOException e1) {
                e1.printStackTrace();
            } finally {
                try {
                    bw.close();
                } catch (IOException e1) {
                    e1.printStackTrace();
                }
            } 
        }
    }
}