chore(samples): refactoring comments. (#528)

* chore (samples) Refactoring comments.

* pr fix: refactored comments.

* 🦉 Updates from OwlBot post-processor

See https://github.com/googleapis/repo-automation-bots/blob/main/packages/owl-bot/README.md

Co-authored-by: Owl Bot <gcf-owl-bot[bot]@users.noreply.github.com>

retail/interactive-tutorials/src/main/java/events/ImportUserEventsBigQuery.java

@@ -38,16 +38,19 @@
 public class ImportUserEventsBigQuery {
 
   public static void main(String[] args) throws IOException, InterruptedException {
-    // TODO(developer): Replace these variables before running the sample.
+    // TODO(developer): Set projectId to your Google Cloud Platform project ID.
     String projectId = ServiceOptions.getDefaultProjectId();
     String defaultCatalog =
         String.format("projects/%s/locations/global/catalogs/default_catalog", projectId);
-    // TO CHECK ERROR HANDLING PASTE THE INVALID CATALOG NAME HERE:
+    // To check error handling use invalid catalog name here:
     // defaultCatalog = "invalid_catalog_name";
+
+    // TODO(developer): Set datasetId to your datasetId
     String datasetId = "user_events";
+    // TODO(developer): Set tableId to your tableId
     String tableId = "events";
-    // TO CHECK ERROR HANDLING USE THE TABLE OF INVALID USER EVENTS:
-    // tableId = "events_some_invalid";
+    // To check error handling use table of invalid user events here:
+    // tableId = "events_some_invalid"
 
     importUserEventsFromBigQuery(projectId, defaultCatalog, datasetId, tableId);
   }

retail/interactive-tutorials/src/main/java/events/PurgeUserEvent.java

@@ -15,7 +15,7 @@
  */
 
 /*
- * Purge user events into a catalog from inline source using Retail API
+ * Deleting user event using Retail API.
  */
 
 package events;
@@ -36,11 +36,11 @@ public class PurgeUserEvent {
 
   public static void main(String[] args)
       throws IOException, ExecutionException, InterruptedException {
-    // TODO(developer): Replace these variables before running the sample.
+    // TODO(developer): Set projectId to your Google Cloud Platform project ID.
     String projectId = ServiceOptions.getDefaultProjectId();
     String defaultCatalog =
         String.format("projects/%s/locations/global/catalogs/default_catalog", projectId);
-    // visitorId generated randomly.
+    // visitorId is generated randomly
     String visitorId = UUID.randomUUID().toString();
 
     callPurgeUserEvents(defaultCatalog, visitorId);
@@ -57,9 +57,11 @@ public static void callPurgeUserEvents(String defaultCatalog, String visitorId)
     try (UserEventServiceClient userEventServiceClient = UserEventServiceClient.create()) {
       PurgeUserEventsRequest purgeUserEventsRequest =
           PurgeUserEventsRequest.newBuilder()
-              // TO CHECK ERROR HANDLING SET INVALID FILTER HERE:
+              // To check error handling set invalid filter here:
               .setFilter(String.format("visitorId=\"%s\"", visitorId))
               .setParent(defaultCatalog)
+              // Setting the force field to true deletes user events. If set to false will return
+              // number of events to be deleted without actually deleting them
               .setForce(true)
               .build();
       System.out.printf("Purge user events request: %s%n", purgeUserEventsRequest);

retail/interactive-tutorials/src/main/java/events/RejoinUserEvent.java

@@ -15,7 +15,7 @@
  */
 
 /*
- * Rejoin user events into a catalog from inline source using Retail API
+ * Starts a user event rejoin operation using Retail API.
  */
 
 package events;
@@ -38,11 +38,11 @@ public class RejoinUserEvent {
 
   public static void main(String[] args)
       throws IOException, ExecutionException, InterruptedException {
-    // TODO(developer): Replace these variables before running the sample.
+    // TODO(developer): Set projectId to your Google Cloud Platform project ID.
     String projectId = ServiceOptions.getDefaultProjectId();
     String defaultCatalog =
         String.format("projects/%s/locations/global/catalogs/default_catalog", projectId);
-    // visitorId generated randomly.
+    // visitorId is generated randomly
     String visitorId = UUID.randomUUID().toString();
 
     callRejoinUserEvents(defaultCatalog, visitorId);

retail/interactive-tutorials/src/main/java/events/WriteUserEvent.java

@@ -15,7 +15,7 @@
  */
 
 /*
- * Write user events into a catalog from inline source using Retail API
+ * Write user event using Retail API.
  */
 
 package events;
@@ -36,11 +36,11 @@ public class WriteUserEvent {
 
   public static void main(String[] args)
       throws IOException, ExecutionException, InterruptedException {
-    // TODO(developer): Replace these variables before running the sample.
+    // TODO(developer): Set projectId to your Google Cloud Platform project ID.
     String projectId = ServiceOptions.getDefaultProjectId();
     String defaultCatalog =
         String.format("projects/%s/locations/global/catalogs/default_catalog", projectId);
-    // visitorId generated randomly.
+    // visitorId is generated randomly
     String visitorId = UUID.randomUUID().toString();
 
     writeUserEvent(defaultCatalog, visitorId);

retail/interactive-tutorials/src/main/java/product/CrudProduct.java

@@ -15,13 +15,12 @@
  */
 
 /*
- * Create product in a catalog using Retail API
+ * Create, update, get and delete product in a catalog using Retail API.
  */
 
 package product;
 
 import com.google.api.gax.rpc.NotFoundException;
-import com.google.cloud.ServiceOptions;
 import com.google.cloud.retail.v2.CreateProductRequest;
 import com.google.cloud.retail.v2.DeleteProductRequest;
 import com.google.cloud.retail.v2.GetProductRequest;
@@ -37,7 +36,8 @@
 public class CrudProduct {
 
   public static void main(String[] args) throws IOException {
-    String projectId = ServiceOptions.getDefaultProjectId();
+    // TODO(developer): Set projectId to your Google Cloud Platform project ID.
+    String projectId = "my-project";
     String generatedProductId = UUID.randomUUID().toString();
     String branchName =
         String.format(