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Ensure you have Java 8 or higher installed. Verify it by typing this command in your terminal:

java --version

Write a "Hello World" program

The simplest way to begin is with the OpenAI integration. LangChain4j offers integration with many LLMs. Each integration has its own dependency. In this case, we should add the OpenAI dependency:

  • For Maven in pom.xml:
  • For Gradle in build.gradle:
implementation 'dev.langchain4j:langchain4j-open-ai:0.30.0'

Then, import your OpenAI API key. It's recommended to store your API keys in environment variables to reduce the risk of exposing them publicly.

String apiKey = System.getenv("OPENAI_API_KEY");

If you don't have your own OpenAI API key, don't worry. You can temporarily use demo key, which we provide for free for demonstration purposes:

String apiKey = "demo";

Be aware that when using the demo key, all requests to the OpenAI API go through our proxy, which injects the real key before forwarding your request to the OpenAI API. We do not collect or use your data in any way. The demo key has a quota and should only be used for demonstration purposes.

Once you've set up the key, let's create an instance of an OpenAiChatModel:

OpenAiChatModel model = OpenAiChatModel.withApiKey(apiKey);

Now, it is time to chat!

String answer = model.generate("Say 'Hello World'");
System.out.println(answer); // Hello World