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Source Code

agent-client-tutorial/01-create-file

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What You’ll Build

A Java program that asks an agent to create a file, then verifies the file was created. No Spring Boot required — just plain Java with the AgentClient API.

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Step 1: Set Up the Project

Create a Maven project with the Claude agent dependency: 
<dependencies>
    <dependency>
        <groupId>io.github.markpollack</groupId>
        <artifactId>agent-claude</artifactId>
        <version>0.20.0</version>
    </dependency>
</dependencies>
Or clone the tutorial repo: 
git clone https://github.com/markpollack/agent-client-tutorial.git
cd agent-client-tutorial/01-create-file

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Step 2: Understand the Code

Three lines do the real work: 
// 1. Build the model — this is the provider-specific part
ClaudeAgentModel model = ClaudeAgentModel.builder()
    .defaultOptions(ClaudeAgentOptions.builder()
        .model("claude-sonnet-4-5")
        .yolo(true)
        .build())
    .build();

// 2. Create the client — this is the portable part
AgentClient client = AgentClient.create(model);

// 3. Run a goal
AgentClientResponse response = client.run(
    "Create a file named hello.txt with the content 'Hello from Agent Client!'"
);
Notice the separation:
  • Model construction is provider-specific (you import ClaudeAgentModel)
  • Client usage is portable (AgentClient.create() and .run() work with any model)
  • The goal is a plain English string — describe what, not how

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Step 3: Run It

./mvnw compile exec:java -Dexec.mainClass="HelloAgent"

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Step 4: Verify

Check that hello.txt was created: 
cat hello.txt
# Output: Hello from Agent Client!

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What Just Happened

  1. ClaudeAgentModel found the Claude CLI on your system
  2. AgentClient.create(model) wrapped it in the portable client API
  3. .run(goal) sent your English instruction to the Claude CLI
  4. The CLI created the file, and the response told you it succeeded
The agent did the same thing a developer would do — it created a file. The difference is you described what to do, not how.

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Next

Lesson 2: Multi-Provider → — Run this same task with Codex and Gemini without changing the client code.