Time for action – persisting a value

To save and load preferences, an instance of Preferences (from the org.osgi.service.prefs package) is typically obtained from an instance of InstanceScope (from the org.eclipse.core.runtime.preferences package). The INSTANCE singleton returns an instance of Preferences that has a getNode method. This returns a store that can be used to persist key/value pairs.

1. Open the Activator of the com.packtpub.e4.clock.ui plug-in.

2. Add the following to the start method to count the number of times the plug-in has been launched:

   // import org.osgi.service.prefs.Preferences;
   // import org.eclipse.core.runtime.preferences.InstanceScope;
   // ^ add these if necessary to top of the class
   Preferences preferences =
    InstanceScope.INSTANCE.getNode("com.packtpub.e4.clock.ui");
   int launchCount = preferences.getInt("launchCount", 0)+1;
   System.out.println("I have been launched "+launchCount+" times");
   preferences.putInt("launchCount", launchCount);
   preferences.sync();

3. Run the target...