How to Call OpenAI API in Java (Step-by-Step Guide)

Artificial Intelligence is rapidly becoming a core part of modern applications. If you’re a Java developer, integrating AI into your application might sound complex—but it’s actually very simple with the OpenAI API.

In this guide, we’ll walk through how to call the OpenAI API in Java step-by-step, using Maven and clean, beginner-friendly code.

By the end of this tutorial, you’ll be able to:

Connect Java with OpenAI
Send prompts and receive AI responses
Build your own AI-powered features

How to Call OpenAI API in Java (Step-by-Step Guide)

⚙️ Prerequisites

Before we start, make sure you have:

Java 8 or above installed
Maven installed
An OpenAI API key

👉 You can get your API key from the OpenAI platform.

📦 Step 1: Add Maven Dependency

We will use Java’s built-in HTTP client (no external SDK needed).

Add this dependency if you’re using Java 11+ (for HTTP client support):

</dependency>

</dependencies>

🏗️ Step 2: Create Java Class

Create a class in package:

package com.kscodes.ai;

💻 Step 3: Write Code to Call OpenAI API

Here’s a simple example to call the OpenAI API:

package com.kscodes.ai;

import java.io.IOException;

import java.net.URI;

import java.net.http.HttpClient;

import java.net.http.HttpRequest;

import java.net.http.HttpResponse;

import org.json.JSONArray;

import org.json.JSONObject;

public class OpenAIExample {

private static final String API_KEY = "YOUR_API_KEY";

public static void main(String[] args) throws IOException, InterruptedException {

String prompt = "Explain Java in simple terms";

JSONObject requestBody = new JSONObject();

requestBody.put("model", "gpt-4o-mini");

JSONArray messages = new JSONArray();

JSONObject message = new JSONObject();

message.put("role", "user");

message.put("content", prompt);

messages.put(message);

requestBody.put("messages", messages);

HttpRequest request = HttpRequest.newBuilder()

.uri(URI.create("https://api.openai.com/v1/chat/completions"))

.header("Content-Type", "application/json")

.header("Authorization", "Bearer " + API_KEY)

.POST(HttpRequest.BodyPublishers.ofString(requestBody.toString()))

.build();

HttpClient client = HttpClient.newHttpClient();

HttpResponse<String> response = client.send(request, HttpResponse.BodyHandlers.ofString());

JSONObject jsonResponse = new JSONObject(response.body());

String result = jsonResponse

.getJSONArray("choices")

.getJSONObject(0)

.getJSONObject("message")

.getString("content");

System.out.println("AI Response: " + result);

}

▶️ Step 4: Run the Application

Replace "YOUR_API_KEY" with your actual API key
Run the program

You will see an AI-generated response printed in your console 🎉

🔍 How It Works

Here’s what’s happening behind the scenes:

We create a JSON request with:
- Model name (gpt-4o-mini)
- User prompt
We send an HTTP POST request to OpenAI API
OpenAI processes the request and sends back a response
We extract and print the AI-generated text

💡 Tips & Best Practices

🔐 Never hardcode API keys in production (use environment variables)
⚡ Handle exceptions properly for production apps
📊 Add logging for debugging API responses
💰 Monitor API usage to control cost

🎯 Conclusion

Calling the OpenAI API in Java is surprisingly simple. With just a few lines of code, you can integrate powerful AI features into your applications.

This “OpenAI API Java Example” is a great starting point for building:

Chatbots
Content generators
Smart automation tools