Fix spelling mistakes (#859)

diff --git a/rocketmq-iot-bridge/src/main/java/org/apache/rocketmq/iot/example/MqttSampleConsumer.java b/rocketmq-iot-bridge/src/main/java/org/apache/rocketmq/iot/example/MqttSampleConsumer.java
index 50609be..5460769 100644
--- a/rocketmq-iot-bridge/src/main/java/org/apache/rocketmq/iot/example/MqttSampleConsumer.java
+++ b/rocketmq-iot-bridge/src/main/java/org/apache/rocketmq/iot/example/MqttSampleConsumer.java
@@ -35,13 +35,13 @@
         String topic = "mqtt-sample";
         int qos = 0;
         String broker = "tcp://127.0.0.1:1883";
-        String clinetId = "JavaSampleConsumer";
+        String clientId = "JavaSampleConsumer";
 
         MemoryPersistence persistence = new MemoryPersistence();
 
         {
             try {
-                MqttClient sampleClient = new MqttClient(broker, clinetId, persistence);
+                MqttClient sampleClient = new MqttClient(broker, clientId, persistence);
                 MqttConnectOptions connectOptions = new MqttConnectOptions();
                 connectOptions.setCleanSession(true);
                 log.info("Connecting to broker: " + broker);
diff --git a/rocketmq-iot-bridge/src/main/java/org/apache/rocketmq/iot/protocol/mqtt/handler/downstream/impl/MqttConnectMessageHandler.java b/rocketmq-iot-bridge/src/main/java/org/apache/rocketmq/iot/protocol/mqtt/handler/downstream/impl/MqttConnectMessageHandler.java
index 8b6776a..a94a80d 100644
--- a/rocketmq-iot-bridge/src/main/java/org/apache/rocketmq/iot/protocol/mqtt/handler/downstream/impl/MqttConnectMessageHandler.java
+++ b/rocketmq-iot-bridge/src/main/java/org/apache/rocketmq/iot/protocol/mqtt/handler/downstream/impl/MqttConnectMessageHandler.java
@@ -59,7 +59,7 @@
             // protocol violation and disconnect
             ctx.fireUserEventTriggered(new DisconnectChannelEvent(ctx.channel()));
             return;
-        } else if (!isServiceAviable(connectMessage)) {
+        } else if (!isAvailable(connectMessage)) {
             returnCode = MqttConnectReturnCode.CONNECTION_REFUSED_SERVER_UNAVAILABLE;
         } else {
             client.setId(connectMessage.payload().clientIdentifier());
@@ -73,7 +73,7 @@
         ctx.writeAndFlush(ackMessage);
     }
 
-    private boolean isServiceAviable(MqttConnectMessage connectMessage) {
+    private boolean isAvailable(MqttConnectMessage connectMessage) {
         int version = connectMessage.variableHeader().version();
         return version >= MIN_AVAILABLE_VERSION && version <= MAX_AVAILABLE_VERSION;
     }