Get before increment when getting a new callback id; add javadocs

Signed-off-by: Andrew Carbonetto <[email protected]>

java/client/src/main/java/glide/connectors/handlers/CallbackDispatcher.java

@@ -50,9 +50,9 @@ public Pair<Integer, CompletableFuture<Response>> registerRequest() {
     var future = new CompletableFuture<Response>();
     Integer callbackId = freeRequestIds.poll();
     if (callbackId == null) {
-      // on null, we have no available request ids available
-      // we can add
-      callbackId = nextAvailableRequestId.incrementAndGet();
+      // on null, we have no available request ids available in freeRequestIds
+      // instead, get the next available request from counter
+      callbackId = nextAvailableRequestId.getAndIncrement();
     }
     responses.put(callbackId, future);
     return Pair.of(callbackId, future);

java/client/src/main/java/glide/managers/CommandManager.java

@@ -9,6 +9,10 @@
 import redis_request.RedisRequestOuterClass.RequestType;
 import response.ResponseOuterClass.Response;
 
+/**
+ * Service responsible for submitting command requests to a socket channel handler
+ * and unpack responses from the same socket channel handler.
+ */
 @RequiredArgsConstructor
 public class CommandManager {
 
@@ -53,7 +57,7 @@ private CompletableFuture<String> submitNewRequest(RequestType command, List<Str
    * Check response and extract data from it.
    *
    * @param response A response received from rust core lib
-   * @return A String from the Redis RESP2 response, or Ok. Otherwise, returns null
+   * @return A String from the Redis response, or Ok. Otherwise, returns null
    */
   private String extractValueFromGlideRsResponse(Response response) {
     if (response.hasRequestError()) {

java/client/src/main/java/glide/managers/ConnectionManager.java

@@ -10,6 +10,10 @@
 import response.ResponseOuterClass.ConstantResponse;
 import response.ResponseOuterClass.Response;
 
+/**
+ * Service responsible for submitting connection requests to a socket channel handler
+ * and unpack responses from the same socket channel handler.
+ */
 @RequiredArgsConstructor
 public class ConnectionManager {