Add checkstyle validation and fix style violations in the pulsar clie…

…nt api module (#5115)

### Modifications

The following changes were made in this pull request:

* Configured the checkstyle plugin
* Fixed reported style violations

This pull request has only cosmetic changes in the pulsar client api module and shouldn't introduce any change in the business logic.

pulsar-client-api/pom.xml

@@ -40,4 +40,28 @@
         <scope>provided</scope>
       </dependency>
     </dependencies>
+
+    <build>
+        <plugins>
+            <plugin>
+                <groupId>org.apache.maven.plugins</groupId>
+                <artifactId>maven-checkstyle-plugin</artifactId>
+                <executions>
+                    <execution>
+                        <id>check-style</id>
+                        <phase>verify</phase>
+                        <configuration>
+                            <configLocation>../buildtools/src/main/resources/pulsar/checkstyle.xml</configLocation>
+                            <suppressionsLocation>../buildtools/src/main/resources/pulsar/suppressions.xml</suppressionsLocation>
+                            <encoding>UTF-8</encoding>
+                        </configuration>
+                        <goals>
+                            <goal>check</goal>
+                        </goals>
+                    </execution>
+                </executions>
+            </plugin>
+        </plugins>
+    </build>
+
 </project>

pulsar-client-api/src/main/java/org/apache/pulsar/client/api/Authentication.java

@@ -50,7 +50,6 @@ default AuthenticationDataProvider getAuthData() throws PulsarClientException {
     }
 
     /**
-     *
      * Get/Create an authentication data provider which provides the data that this client will be sent to the broker.
      * Some authentication method need to auth between each client channel. So it need the broker, who it will talk to.
      *
@@ -64,7 +63,7 @@ default AuthenticationDataProvider getAuthData(String brokerHostName) throws Pul
     }
 
     /**
-     * Configure the authentication plugins with the supplied parameters
+     * Configure the authentication plugins with the supplied parameters.
      *
      * @param authParams
      * @deprecated This method will be deleted on version 2.0, instead please use configure(String
@@ -75,7 +74,7 @@ default AuthenticationDataProvider getAuthData(String brokerHostName) throws Pul
     void configure(Map<String, String> authParams);
 
     /**
-     * Initialize the authentication provider
+     * Initialize the authentication provider.
      */
     void start() throws PulsarClientException;
 
@@ -91,7 +90,7 @@ default void authenticationStage(String requestUrl,
     }
 
     /**
-     * Add an authenticationStage that will complete along with authFuture
+     * Add an authenticationStage that will complete along with authFuture.
      */
     default Set<Entry<String, String>> newRequestHeader(String hostName,
                                                         AuthenticationDataProvider authData,

pulsar-client-api/src/main/java/org/apache/pulsar/client/api/AuthenticationDataProvider.java

@@ -31,7 +31,7 @@
 import org.apache.pulsar.common.api.AuthData;
 
 /**
- * Interface for accessing data which are used in variety of authentication schemes on client side
+ * Interface for accessing data which are used in variety of authentication schemes on client side.
  */
 public interface AuthenticationDataProvider extends Serializable {
     /*
@@ -78,7 +78,7 @@ default boolean hasDataForHttp() {
 
     /**
      *
-     * @return a authentication scheme, or <code>null<c/ode> if the request will not be authenticated
+     * @return a authentication scheme, or {@code null} if the request will not be authenticated.
      */
     default String getHttpAuthType() {
         return null;
@@ -118,7 +118,7 @@ default String getCommandData() {
      * then returns null if authentication has completed;
      * returns authenticated data back to server side, if authentication has not completed.
      *
-     * Mainly used for mutual authentication like sasl.
+     * <p>Mainly used for mutual authentication like sasl.
      */
     default AuthData authenticate(AuthData data) throws AuthenticationException {
         byte[] bytes = (hasDataFromCommand() ? this.getCommandData() : "").getBytes(UTF_8);

pulsar-client-api/src/main/java/org/apache/pulsar/client/api/AuthenticationFactory.java

@@ -52,6 +52,8 @@ public static Authentication token(Supplier<String> tokenSupplier) {
         return DefaultImplementation.newAuthenticationToken(tokenSupplier);
     }
 
+    // CHECKSTYLE.OFF: MethodName
+
     /**
      * Create an authentication provider for TLS based authentication.
      *
@@ -65,6 +67,8 @@ public static Authentication TLS(String certFilePath, String keyFilePath) {
         return DefaultImplementation.newAuthenticationTLS(certFilePath, keyFilePath);
     }
 
+    // CHECKSTYLE.ON: MethodName
+
     /**
      * Create an instance of the {@link Authentication} object by using
      * the plugin class name.
@@ -86,14 +90,14 @@ public static Authentication create(String authPluginClassName, String authParam
     }
 
     /**
-     * Create an instance of the Authentication-Plugin
+     * Create an instance of the Authentication-Plugin.
      *
      * @param authPluginClassName name of the Authentication-Plugin you want to use
      * @param authParams          map which represents parameters for the Authentication-Plugin
      * @return instance of the Authentication-Plugin
      * @throws UnsupportedAuthenticationException
      */
-    public static final Authentication create(String authPluginClassName, Map<String, String> authParams)
+    public static Authentication create(String authPluginClassName, Map<String, String> authParams)
             throws UnsupportedAuthenticationException {
         try {
             return DefaultImplementation.createAuthentication(authPluginClassName, authParams);

pulsar-client-api/src/main/java/org/apache/pulsar/client/api/BatchMessageContainer.java

@@ -19,7 +19,7 @@
 package org.apache.pulsar.client.api;
 
 /**
- * Batch message container for individual messages being published until they are batched and sent to broker
+ * Batch message container for individual messages being published until they are batched and sent to broker.
  */
 public interface BatchMessageContainer {
 
@@ -57,7 +57,7 @@ public interface BatchMessageContainer {
     void discard(Exception ex);
 
     /**
-     * Return the batch container batch message in multiple batches
+     * Return the batch container batch message in multiple batches.
      * @return
      */
     boolean isMultiBatches();

pulsar-client-api/src/main/java/org/apache/pulsar/client/api/BatcherBuilder.java

@@ -18,33 +18,32 @@
  */
 package org.apache.pulsar.client.api;
 
-import org.apache.pulsar.client.internal.DefaultImplementation;
-
 import java.io.Serializable;
+import org.apache.pulsar.client.internal.DefaultImplementation;
 
 /**
- * Batcher builder
+ * Batcher builder.
  */
 public interface BatcherBuilder extends Serializable {
 
     /**
-     * Default batch message container
+     * Default batch message container.
      *
-     * incoming single messages:
+     * <p>incoming single messages:
      * (k1, v1), (k2, v1), (k3, v1), (k1, v2), (k2, v2), (k3, v2), (k1, v3), (k2, v3), (k3, v3)
      *
-     * batched into single batch message:
+     * <p>batched into single batch message:
      * [(k1, v1), (k2, v1), (k3, v1), (k1, v2), (k2, v2), (k3, v2), (k1, v3), (k2, v3), (k3, v3)]
      */
     BatcherBuilder DEFAULT = DefaultImplementation.newDefaultBatcherBuilder();
 
     /**
-     * Key based batch message container
+     * Key based batch message container.
      *
-     * incoming single messages:
+     * <p>incoming single messages:
      * (k1, v1), (k2, v1), (k3, v1), (k1, v2), (k2, v2), (k3, v2), (k1, v3), (k2, v3), (k3, v3)
      *
-     * batched into multiple batch messages:
+     * <p>batched into multiple batch messages:
      * [(k1, v1), (k1, v2), (k1, v3)], [(k2, v1), (k2, v2), (k2, v3)], [(k3, v1), (k3, v2), (k3, v3)]
      */
     BatcherBuilder KEY_BASED = DefaultImplementation.newKeyBasedBatcherBuilder();