[Doc] Add descriptions for numListenerThreads (apache#9525)

* [Doc] Add descriptions for numListenerThreads

* update

site2/docs/client-libraries-java.md

@@ -107,7 +107,7 @@ String | `authParams` | String represents parameters for the authentication plug
 long|`operationTimeoutMs`|Operation timeout |30000
 long|`statsIntervalSeconds`|Interval between each stats info<br/><br/>Stats is activated with positive `statsInterval`<br/><br/>Set `statsIntervalSeconds` to 1 second at least |60
 int|`numIoThreads`| The number of threads used for handling connections to brokers | 1 
-int|`numListenerThreads`|The number of threads used for handling message listeners | 1 
+int|`numListenerThreads`|The number of threads used for handling message listeners. The listener thread pool is shared across all the consumers and readers using the "listener" model to get messages. For a given consumer, the listener is always invoked from the same thread to ensure ordering. If you want multiple threads to process a single topic, you need to create a [`shared`](https://pulsar.apache.org/docs/en/next/concepts-messaging/#shared) subscription and multiple consumers for this subscription. This does not ensure ordering.| 1 
 boolean|`useTcpNoDelay`|Whether to use TCP no-delay flag on the connection to disable Nagle algorithm |true
 boolean |`useTls` |Whether to use TLS encryption on the connection| false
 string | `tlsTrustCertsFilePath` |Path to the trusted TLS certificate file|None