利用properties文件記錄界面的大小和位置

class PropertiesFrame extends JFrame {
 public PropertiesFrame() {
  String userDir = System.getProperty("user.home");
  File propertiesDir = new File(userDir, ".coreJava");
  if(!propertiesDir.exists()) {
   propertiesDir.mkdir();
  }
  propertiesFile = new File(propertiesDir, "program.properties");
  
  Properties defaultSetting = new Properties();
  defaultSetting.put("left", "0");
  defaultSetting.put("top", "0");
  defaultSetting.put("width", "" + DEFAULT_WIDTH);
  defaultSetting.put("height", "" + DEFAULT_HEIGHT);
  defaultSetting.put("title", "");
  
  settings = new Properties(defaultSetting);
  if(propertiesFile.exists()) {
   try {
    FileInputStream in = new FileInputStream(propertiesFile);
    settings.load(in);
    in.close();
   } catch (Exception e) {
    e.printStackTrace();
   }
  }
  
  int left = Integer.parseInt(settings.getProperty("left"));
  int top = Integer.parseInt(settings.getProperty("top"));
  int width = Integer.parseInt(settings.getProperty("width"));
  int height = Integer.parseInt(settings.getProperty("height"));
  setBounds(left, top, width, height);
  
  String title  = settings.getProperty("title");
  if("".equals(title)) {
   title = JOptionPane.showInputDialog("Please input a frame title:");
  }
  if(null == title) {
   title = "";
  }
  setTitle(title);
  
  addWindowListener(new WindowAdapter() {
   public void windowClosing(WindowEvent event) {
    settings.put("left", "" + getX());
    settings.put("top", "" + getY());
    settings.put("width", "" + getWidth());
    settings.put("height", "" + getHeight());
    settings.put("title", getTitle());
    
    try {
     FileOutputStream out = new FileOutputStream(propertiesFile);
     settings.store(out, "program properties");
     out.close();
    } catch (Exception e) {
     e.printStackTrace();
    }
    
    System.exit(0);
   }
  });
 }
 
 public static final int DEFAULT_WIDTH = 300;
 public static final int DEFAULT_HEIGHT = 200;
 
 private File propertiesFile;
 private Properties settings;
}