✨ 代码优化。

mica-mqtt-codec/src/main/java/net/dreamlu/iot/mqtt/codec/MqttMessageBuilders.java

@@ -340,7 +340,7 @@ public final class MqttMessageBuilders {
 		private Long maximumPacketSize;
 		private int topicAliasMaximum;
 		private String reasonString;
-		private MqttProperties.UserProperties userProperties = new MqttProperties.UserProperties();
+		private final MqttProperties.UserProperties userProperties = new MqttProperties.UserProperties();
 		private Boolean wildcardSubscriptionAvailable;
 		private Boolean subscriptionIdentifiersAvailable;
 		private Boolean sharedSubscriptionAvailable;

mica-mqtt-codec/src/main/java/net/dreamlu/iot/mqtt/codec/MqttVersion.java

@@ -65,11 +65,11 @@ public enum MqttVersion {
 				mv = MQTT_5;
 				break;
 			default:
-				throw new MqttUnacceptableProtocolVersionException(protocolName + "is unknown protocol name");
+				throw new MqttUnacceptableProtocolVersionException(protocolName + " is an unknown protocol name");
 		}
 		if (mv.name.equals(protocolName)) {
 			return mv;
 		}
-		throw new MqttUnacceptableProtocolVersionException(protocolName + " and " + protocolLevel + " are not match");
+		throw new MqttUnacceptableProtocolVersionException(protocolName + " and " + protocolLevel + " don't match");
 	}
 }