[doc] Add code samples for Protobuf and Avro schemas in java documentation

site2/docs/client-libraries-java.md

@@ -593,15 +593,31 @@ The following schema formats are currently available for Java:
         .topic("some-string-topic")
         .create();
   ```
-* JSON schemas can be created for POJOs using the `JSONSchema` class. Here's an example:
+
+* JSON schemas can be created for POJOs using `Schema.JSON`. Here's an example:
 
   ```java
-  Schema<MyPojo> pojoSchema = JSONSchema.of(MyPojo.class);
-  Producer<MyPojo> pojoProducer = client.newProducer(pojoSchema)
+  Producer<MyPojo> pojoProducer = client.newProducer(Schema.JSON(MyPojo.class))
         .topic("some-pojo-topic")
         .create();
   ```
 
+* Protobuf schemas can be generate using `Schema.PROTOBUF`. The following example shows how to create the Protobuf schema and use it to instantiate a new producer:
+
+  ```java
+  Producer<MyProtobuf> protobufProducer = client.newProducer(Schema.PROTOBUF(MyProtobuf.class))
+        .topic("some-protobuf-topic")
+        .create();
+  ```
+
+* Avro schemas can be defined with the help of `Schema.AVRO`. The next code snippet demonstrates the creation and usage of the Avro schema:
+
+  ```java
+  Producer<MyAvro> avroProducer = client.newProducer(Schema.AVRO(MyAvro.class))
+        .topic("some-avro-topic")
+        .create();
+  ```
+
 ## Authentication
 
 Pulsar currently supports two authentication schemes: [TLS](security-tls-authentication.md) and [Athenz](security-athenz.md). The Pulsar Java client can be used with both.