feat: add sample agent providing currency conversion to demonstrate multi-turn dialogue and streaming responses.

Author: cmtoan

samples/java/agents/currency_exchange_rates/README.md

@@ -1,12 +1,12 @@
 # Currency Exchange Rates
 
-This sample demonstrates a currency conversion agent exposed through the A2A protocol. 
+This sample demonstrates a currency conversion agent exposed through the A2A protocol.
 It showcases conversational interactions with support for multi-turn dialogue and streaming responses.
 The agent is written using Quarkus LangChain4j and makes use of the [A2A Java](https://github.com/a2aproject/a2a-java) SDK.
 
 ## How It Works
 
-This agent uses an Ollama LLM (for example, qwen2.5:7b) to provide currency exchange information. 
+This agent uses an Ollama LLM (for example, qwen2.5:7b) to provide currency exchange information.
 The A2A protocol enables standardized interaction with the agent, allowing clients to send requests and receive real-time updates.
 
 ```mermaid
@@ -51,7 +51,7 @@ sequenceDiagram
 
 - Java 17 or higher
 - Access to an LLM (Ollama)
-- Ollama installed (see https://ollama.com/download)
+- Ollama installed (see [Download Ollama](https://ollama.com/download))
 
 ## Running the Sample
 
@@ -60,7 +60,7 @@ which is in the `client` directory.
 
 ### Running Ollama
 
-1. Launch the Ollama server by default on port 11434 (http://localhost:11434)
+1. Launch the Ollama server by default on port 11434 ([Local Ollama server](http://localhost:11434))
 
     ```bash
    ollama serve
@@ -72,15 +72,15 @@ which is in the `client` directory.
    ollama pull qwen2.5:7b
    ollama run qwen2.5:7b
     ```
-   
+
 ### Running the A2A Server Agent
 
 1. Navigate to the `currency_exchange_rates` sample directory:
 
     ```bash
     cd samples/java/agents/currency_exchange_rates/server
     ```
-   
+
 2. Start the A2A server agent
 
    **NOTE:**
@@ -90,7 +90,7 @@ which is in the `client` directory.
    ```bash
    mvn quarkus:dev
    ```
-   
+
 ### Running the A2A Java Client
 
 The Java `TestClient` communicates with the Currency Agent using the A2A Java SDK.

samples/java/agents/currency_exchange_rates/client/src/main/java/com/samples/a2a/client/TestClient.java

@@ -77,32 +77,40 @@ public static void main(final String[] args) {
         .build();
 
       // Create and send the message without INPUT_REQUIRED
-      StreamingClient streamingClient = getStreamingClient(publicAgentCard,
-        clientConfig);
-      sendMessage(streamingClient.client(), "how much is 10 USD in INR?",
-        null, null, streamingClient.messageResponse());
+      runSingleTurnDemo(publicAgentCard, clientConfig);
 
       // Create and send the message with INPUT_REQUIRED
-      StreamingClient streamingClient1 = getStreamingClient(publicAgentCard,
-        clientConfig);
-      StreamingClient streamingClient2 = getStreamingClient(publicAgentCard,
-        clientConfig);
-
-      MessageResponse message1 = sendMessage(streamingClient1.client(),
-        "How much is the exchange rate for 1 USD?", null, null,
-        streamingClient1.messageResponse());
-
-      // Resubscribe to a task to send additional information for this task
-      streamingClient2.client().resubscribe(new TaskIdParams(message1.taskId()),
-        streamingClient2.consumers(), streamingClient2.streamingErrorHandler());
-      sendMessage(streamingClient2.client(), "CAD", message1.contextId(),
-        message1.taskId(), streamingClient2.messageResponse());
+      runMultiTurnDemo(publicAgentCard, clientConfig);
     } catch (Exception e) {
       System.err.println("An error occurred: " + e.getMessage());
       e.printStackTrace();
     }
   }
 
+  private static void runMultiTurnDemo(AgentCard publicAgentCard, ClientConfig clientConfig) {
+    StreamingClient streamingClient1 = getStreamingClient(publicAgentCard,
+      clientConfig);
+    StreamingClient streamingClient2 = getStreamingClient(publicAgentCard,
+      clientConfig);
+
+    MessageResponse message1 = sendMessage(streamingClient1.client(),
+      "How much is the exchange rate for 1 USD?", null, null,
+      streamingClient1.messageResponse());
+
+    // Resubscribe to a task to send additional information for this task
+    streamingClient2.client().resubscribe(new TaskIdParams(message1.taskId()),
+      streamingClient2.consumers(), streamingClient2.streamingErrorHandler());
+    sendMessage(streamingClient2.client(), "CAD", message1.contextId(),
+      message1.taskId(), streamingClient2.messageResponse());
+  }
+
+  private static void runSingleTurnDemo(AgentCard publicAgentCard, ClientConfig clientConfig) {
+    StreamingClient streamingClient = getStreamingClient(publicAgentCard,
+      clientConfig);
+    sendMessage(streamingClient.client(), "how much is 10 USD in INR?",
+      null, null, streamingClient.messageResponse());
+  }
+
   private static StreamingClient getStreamingClient(
     final AgentCard publicAgentCard, final ClientConfig clientConfig) {
     // Create a CompletableFuture to handle async response

samples/java/agents/currency_exchange_rates/server/src/main/java/com/samples/a2a/server/CurrencyAgent.java

@@ -52,6 +52,7 @@ public interface CurrencyAgent {
     3. Never assume or guess the target currency.
     4. Never provide an answer until all required currencies are explicitly
     stated.
+    5. You must replace all placeholders with real values.
     """)
   ResponseFormat handleRequest(@UserMessage String question);
 }