[doc] Add setter for reader subscription name (apache#10027)

* add setter for reader sub

* update

site2/docs/client-libraries-java.md

@@ -667,6 +667,7 @@ In the example above, a `Reader` object is instantiated for a specific topic and
 
 The code sample above shows pointing the `Reader` object to a specific message (by ID), but you can also use `MessageId.earliest` to point to the earliest available message on the topic of `MessageId.latest` to point to the most recent available message.
 
+### Configure reader
 When you create a reader, you can use the `loadConf` configuration. The following parameters are available in `loadConf`.
 
 | Type | Name | <div style="width:300px">Description</div> | Default
@@ -675,6 +676,8 @@ String|`topicName`|Topic name. |None
 int|`receiverQueueSize`|Size of a consumer's receiver queue.<br/><br/>For example, the number of messages that can be accumulated by a consumer before an application calls `Receive`.<br/><br/>A value higher than the default value increases consumer throughput, though at the expense of more memory utilization.|1000
 ReaderListener&lt;T&gt;|`readerListener`|A listener that is called for message received.|None
 String|`readerName`|Read name.|null
+String| `subscriptionName`|Subscription name|When there is a single topic, the default subscription name is `"reader-" + 10-digit UUID`.
+When there are multiple topics, the default subscription name is `"multiTopicsReader-" + 10-digit UUID`.
 String|`subscriptionRolePrefix`|Prefix of subscription role. |null
 CryptoKeyReader|`cryptoKeyReader`|Interface that abstracts the access to a key store.|null
 ConsumerCryptoFailureAction|`cryptoFailureAction`|Consumer should take action when it receives a message that can not be decrypted.<br/><br/><li>**FAIL**: this is the default option to fail messages until crypto succeeds.</li><br/><li> **DISCARD**: silently acknowledge and not deliver message to an application.</li><br/><li>**CONSUME**: deliver encrypted messages to applications. It is the application's responsibility to decrypt the message.<br/><br/>The message decompression fails. <br/><br/>If messages contain batch messages, a client is not be able to retrieve individual messages in batch.<br/><br/>Delivered encrypted message contains {@link EncryptionContext} which contains encryption and compression information in it using which application can decrypt consumed message payload.|ConsumerCryptoFailureAction.FAIL</li>