Sonar fixes

* use equals
* inner assignment
* local before return
* unnecessary locals
* catch and throw
* uninstantiable with no statics
* implement `Serializable` in `Comparator` to enable `TreeMap` serialization
* exceptions as flow control

spring-integration-redis/src/main/java/org/springframework/integration/redis/inbound/RedisQueueInboundGateway.java

@@ -319,7 +319,8 @@ public class RedisQueueInboundGateway extends MessagingGatewaySupport implements
 	@Override
 	protected void doStop() {
 		super.doStop();
-		this.active = this.listening = false;
+		this.active = false;
+		this.listening = false;
 	}
 
 	public boolean isListening() {