Conditionally create the derived container if it hasn't been already created

CallGemma.java

package gemini.workshop;

import dev.langchain4j.model.chat.ChatLanguageModel;
import dev.langchain4j.model.ollama.OllamaChatModel;
import org.testcontainers.ollama.OllamaContainer;
import org.testcontainers.utility.DockerImageName;

import java.io.IOException;

public class CallGemma {

    private static final String TC_OLLAMA_GEMMA_2_B = "tc-ollama-gemma-2b";

    private static class CreateGemmaOllamaContainer {
        public static void main(String[] args) throws IOException, InterruptedException {
            // Creating an Ollama container with Gemma 2B, only once
            try (OllamaContainer ollama = new OllamaContainer("ollama/ollama:0.1.26")) {
                ollama.start();
                ollama.execInContainer("ollama", "pull", "gemma:2b");
                ollama.commitToImage(TC_OLLAMA_GEMMA_2_B);
            }
        }
    }

    public static void main(String[] args) throws IOException, InterruptedException {
        try (
            // Image substitution to use our new Gemma-based Ollama image instead of the default Ollama image
            OllamaContainer ollama = new OllamaContainer(
                DockerImageName.parse(TC_OLLAMA_GEMMA_2_B).asCompatibleSubstituteFor("ollama/ollama"))) {

            ollama.start();

            ChatLanguageModel model = OllamaChatModel.builder()
                .baseUrl(String.format("http://%s:%d", ollama.getHost(), ollama.getFirstMappedPort()))
                .modelName("gemma:2b")
                .build();

            String response = model.generate("Why is the sky blue?");

            System.out.println(response);
        }
    }
}