zdm/event-bus
zdm/event-bus
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Add double checked synchronization to EventBus instance initializer

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This commit is contained in:
Kai S. K. Engelbart 2020-09-24 17:41:08 +02:00
parent 603a838640
commit dbb816c6cb
Signed by: kske
GPG Key ID: 8BEB13EC5DF7EF13
1 changed files with 10 additions and 6 deletions
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12
src/main/java/dev/kske/eventbus/EventBus.java
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@ -19,7 +19,7 @@ import java.util.concurrent.ConcurrentHashMap;
*/ */
public final class EventBus { public final class EventBus {
private static EventBus singletonInstance; private static volatile EventBus singletonInstance;
private static final Logger logger = System.getLogger(EventBus.class.getName()); private static final Logger logger = System.getLogger(EventBus.class.getName());
@ -30,11 +30,15 @@ public final class EventBus {
* @since 0.0.2 * @since 0.0.2
*/ */
public static EventBus getInstance() { public static EventBus getInstance() {
if (singletonInstance == null) { EventBus instance = singletonInstance;
if (instance == null)
synchronized (EventBus.class) {
if ((instance = singletonInstance) == null) {
logger.log(Level.DEBUG, "Initializing singleton event bus instance"); logger.log(Level.DEBUG, "Initializing singleton event bus instance");
singletonInstance = new EventBus(); instance = singletonInstance = new EventBus();
} }
return singletonInstance; }
return instance;
} }
private final Map<Class<? extends IEvent>, TreeSet<EventHandler>> bindings private final Map<Class<? extends IEvent>, TreeSet<EventHandler>> bindings