event-bus-core/src/main/java/dev/kske/eventbus/core/EventBus.java

@@ -52,18 +52,26 @@ public final class EventBus {
 	 */
 	public static final int DEFAULT_PRIORITY = 100;
 
-	private static final EventBus singletonInstance = new EventBus();
+	private static volatile EventBus singletonInstance;
 
 	private static final Logger logger = System.getLogger(EventBus.class.getName());
 
 	/**
-	 * Returns the default event bus, which is a statically initialized singleton instance.
+	 * Produces a singleton instance of the event bus. It is lazily initialized on the first call.
 	 *
-	 * @return the default event bus
+	 * @return a singleton instance of the event bus.
 	 * @since 0.0.2
 	 */
 	public static EventBus getInstance() {
-		return singletonInstance;
+		EventBus instance = singletonInstance;
+		if (instance == null)
+			synchronized (EventBus.class) {
+				if ((instance = singletonInstance) == null) {
+					logger.log(Level.DEBUG, "Initializing singleton event bus instance");
+					instance = singletonInstance = new EventBus();
+				}
+			}
+		return instance;
 	}
 
 	private final Map<Class<?>, TreeSet<EventHandler>>	bindings			=