org.argeo.init/src/org/argeo/init/prefs/ThinPreferencesFactory.java

   1 package org.argeo.init.prefs;
   2
   3 import java.util.concurrent.CompletableFuture;
   4 import java.util.concurrent.ExecutionException;
   5 import java.util.prefs.Preferences;
   6 import java.util.prefs.PreferencesFactory;
   7
   8 public class ThinPreferencesFactory implements PreferencesFactory {
   9         private static CompletableFuture<ThinPreferencesFactory> INSTANCE = new CompletableFuture<>();
  10
  11         private SystemRootPreferences systemRootPreferences;
  12
  13         public ThinPreferencesFactory() {
  14                 systemRootPreferences = new SystemRootPreferences();
  15                 if (INSTANCE.isDone())
  16                         throw new IllegalStateException(
  17                                         "There is already a " + ThinPreferencesFactory.class.getName() + " instance.");
  18                 INSTANCE.complete(this);
  19         }
  20
  21         @Override
  22         public Preferences systemRoot() {
  23                 return systemRootPreferences;
  24         }
  25
  26         @Override
  27         public Preferences userRoot() {
  28                 throw new UnsupportedOperationException();
  29         }
  30
  31         public SystemRootPreferences getSystemRootPreferences() {
  32                 return systemRootPreferences;
  33         }
  34
  35         public static ThinPreferencesFactory getInstance() {
  36                 try {
  37                         return INSTANCE.get();
  38                 } catch (InterruptedException | ExecutionException e) {
  39                         throw new IllegalStateException("Cannot get " + ThinPreferencesFactory.class.getName() + " instance.", e);
  40                 }
  41         }
  42 }