code style(client):polish lite pull consumer code style

client/src/main/java/org/apache/rocketmq/client/impl/consumer/DefaultLitePullConsumerImpl.java

@@ -466,7 +466,7 @@ public class DefaultLitePullConsumerImpl implements MQConsumerInner {
 
     public synchronized void subscribe(String topic, String subExpression) throws MQClientException {
         try {
-            if (topic == null || topic.equals("")) {
+            if (topic == null || "".equals(topic)) {
                 throw new IllegalArgumentException("Topic can not be null or empty.");
             }
             setSubscriptionType(SubscriptionType.SUBSCRIBE);
@@ -485,7 +485,7 @@ public class DefaultLitePullConsumerImpl implements MQConsumerInner {
 
     public synchronized void subscribe(String topic, MessageSelector messageSelector) throws MQClientException {
         try {
-            if (topic == null || topic.equals("")) {
+            if (topic == null || "".equals(topic)) {
                 throw new IllegalArgumentException("Topic can not be null or empty.");
             }
             setSubscriptionType(SubscriptionType.SUBSCRIBE);
@@ -741,7 +741,7 @@ public class DefaultLitePullConsumerImpl implements MQConsumerInner {
                     return;
                 }
 
-                if (consumeRequestCache.size() * defaultLitePullConsumer.getPullBatchSize() > defaultLitePullConsumer.getPullThresholdForAll()) {
+                if ((long) consumeRequestCache.size() * defaultLitePullConsumer.getPullBatchSize() > defaultLitePullConsumer.getPullThresholdForAll()) {
                     scheduledThreadPoolExecutor.schedule(this, PULL_TIME_DELAY_MILLS_WHEN_FLOW_CONTROL, TimeUnit.MILLISECONDS);
                     if ((consumeRequestFlowControlTimes++ % 1000) == 0) {
                         log.warn("The consume request count exceeds threshold {}, so do flow control, consume request count={}, flowControlTimes={}", consumeRequestCache.size(), consumeRequestFlowControlTimes);
@@ -797,11 +797,10 @@ public class DefaultLitePullConsumerImpl implements MQConsumerInner {
                 long pullDelayTimeMills = 0;
                 try {
                     SubscriptionData subscriptionData;
+                    String topic = this.messageQueue.getTopic();
                     if (subscriptionType == SubscriptionType.SUBSCRIBE) {
-                        String topic = this.messageQueue.getTopic();
                         subscriptionData = rebalanceImpl.getSubscriptionInner().get(topic);
                     } else {
-                        String topic = this.messageQueue.getTopic();
                         subscriptionData = FilterAPI.buildSubscriptionData(topic, SubscriptionData.SUB_ALL);
                     }