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Java Preferences API - Tutorial

Lars Vogel

Version 1.2

24.01.2014

Using the preference API in Java

This tutorial gives a introduction into the Java Preference API to save key/value pairs for a Java application.


Table of Contents

1. Java Preferences API
2. Exercise: Using the API
2.1. Create program
2.2. Validate
3. Support this website
3.1. Thank you
3.2. Questions and Discussion
4. Links and Literature
4.1. vogella Resources

1. Java Preferences API

The Java 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.

Note

This Java Preferences API is not indented to save application data, i.e. larger structured 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 actual storage of the data is dependent on the platform.

2. Exercise: Using the API

2.1. Create program

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();
  }
} 

2.2. Validate

Run the program twice. The value of "ID1" should be written with its default value (true) to the command line, as the preference value was deleted at the end of the method. The value of "ID2" and "ID3" should have changed after the first call.

3. Support this website

This tutorial is Open Content under the CC BY-NC-SA 3.0 DE license. Source code in this tutorial is distributed under the Eclipse Public License. See the vogella License page for details on the terms of reuse.

Writing and updating these tutorials is a lot of work. If this free community service was helpful, you can support the cause by giving a tip as well as reporting typos and factual errors.

3.1. Thank you

Please consider a contribution if this article helped you. It will help to maintain our content and our Open Source activities.

3.2. Questions and Discussion

If you find errors in this tutorial, please notify me (see the top of the page). Please note that due to the high volume of feedback I receive, I cannot answer questions to your implementation. Ensure you have read the vogella FAQ as I don't respond to questions already answered there.

4. Links and Literature

4.1. vogella Resources

vogella Training Android and Eclipse Training from the vogella team

Android Tutorial Introduction to Android Programming

GWT Tutorial Program in Java, compile to JavaScript and HTML

Eclipse RCP Tutorial Create native applications in Java

JUnit Tutorial Test your application

Git Tutorial Put all your files in a distributed version control system