Setting up a preferences system

Nowadays, users expect every application to provide a preferences window, in which the user may replace the default settings by his or her preferred custom ones. The existing preferences system that is contained in the JDK is not sufficient, as it can only handle strings, booleans and numbers. SweenJet's preferences system using the SweenJet property framework in order to set up such a system, as this tutorial will show.
  1. Defining the properties
  2. Creating a preferences pane
  3. Saving and restoring preferences

Defining the properties

Firstly, a class is created that bundles all properties together. This class consciously violates the rule of encapsulation, but in this case, this approach makes the code more readable.
import org.municware.sweenjet.prop.FileProperty;
import org.municware.sweenjet.prop.PropertyBundle;
import org.municware.sweenjet.prop.StringProperty;

public class MyConfig {
    private static final MyConfig defaultConfiguration = new MyConfig();
     * The default directory denotes the directory that file
     * choosers etc. are initially set to. The directory is set
     * to system property user.dir by default.
    public final FileProperty defaultDirectory;
     * Holds the user's name.
    public final StringProperty userName;
     * Holds the user's mail address.
    public final StringProperty userMailAddress;
     * Bundles all properties that are defined in this class.
    public PropertyBundle allProperties = new PropertyBundle(
            "My Config""mycfg");
     * Creates a new instance of MyConfig
    public MyConfig() {
        this.defaultDirectory = new FileProperty("directory.default""Default directory",
                "File choosers are automatically set to the default directory.",
                FileProperty.DIRECTORY, new File(System.getProperty("user.dir")));
        this.userName = new StringProperty("""Name",
                "The user's name.", System.getProperty(""));
        this.userMailAddress = new StringProperty("user.mail""E-mail address",
                "The user's e-mail address.""");
    public void load(InputStream inthrows IOException {
    public void store(OutputStream outthrows IOException {;
    public static MyConfig getDefault() {
        return defaultConfiguration;

Creating a preferences pane

Saving and restoring preferences

The preferences can be edited by the user. You can save them to the disk so that the settings can be restored when the application restarts.
PropertyBundle uiSettings = new PropertyBundle("UI Settings""ui-settings");
try {
    // The settings path points to the following file:
    // <user.home>/.myapp/1.0-beta/config/<ui-settings>
    File settingsFile = ResourceManager.getSettingsFile("myapp""1.0-beta",
                                                            uiSettings, true);
    InputStream in = new BufferedInputStream(new FileInputStream(settingsFile));
    // Load the ui settings
catch (IOException ex) {