Java Preferences API

The Java Preferences API provides a systematic way to handle user and system preference and configuration data, e.g. to save user settings, remember the last value of a field etc. Information saves with the Java Preference API is stored on the local machine of the user and is available to be re-used in the program, e.g. after a restart of the program.

 

This Java Preferences API is not indented to save application data. The Java Preference API removes the burden from the individual programmer to write code to save configuration values on the different platforms his program may be running.

 

The Preferences API provides a systematic way to handle program preference configurations, e.g. to save user settings, remember the last value of a field etc.

 

Preferences are key / values pairs where the key is an arbitrary name for the preference. The value can be a boolean, string, int of another primitive type. Preferences are received and saved by get and put methods while the get methods also supply a default value in case the preferences is not yet set.

 

The actual storage of the data is dependent on the platform, e.g. under Windows the Windows Registry is used while under Linux a hidden file in the home directory of the user is used.

 

java.util.prefs.Preferences can be easily used. You have to define a node in which the data is stored. Then you can call the getter and setter methods. The second value is the default value, e.g. if the preference value is not set yet, then this value will be used.

 

Create the following program.

 

import java.util.prefs.Preferences;

 

public class PreferenceTest {

           

            private Preferences prefs;

 

            public void setPreference() {

                        // This will define a node in which the preferences can be stored

                        prefs = Preferences.userRoot().node(this.getClass().getName());

                        String ID1 = "Test1";

                        String ID2 = "Test2";

                        String ID3 = "Test3";

 

                        // First we will get the values

                        // Define a boolean value

                        System.out.println(prefs.getBoolean(ID1, true));

                        // Define a string with default "Hello World

                        System.out.println(prefs.get(ID2, "Hello World"));

                        // Define a integer with default 50

                        System.out.println(prefs.getInt(ID3, 50));

 

                        // Now set the values

                        prefs.putBoolean(ID1, false);

                        prefs.put(ID2, "Hello Europa");

                        prefs.putInt(ID3, 45);

 

                        // Delete the preference settings for the first value

                        prefs.remove(ID1);

            }

 

            public static void main(String[] args) {

                        PreferenceTest test = new PreferenceTest();

                        test.setPreference();

            }

}

 

Run the program twice. The value of "ID1" should be still true as we delete it. The value of "ID2" and "ID2" should have changed after the first call.