Telusko Notes

Java Program Structure for OpenAI and Gemini

Both examples are standard Java classes inside the com.telusko package.
Each class contains a main method as the entry point.
The programs use HttpClient, HttpRequest, and HttpResponse from java.net.http.
The main method declares throws IOException, InterruptedException to handle HTTP call issues.
Each class focuses on calling one provider:
- OpenAI for OpenAI APIs
- Gemini for Gemini APIs

Gemini Code

package com.telusko;

import java.io.IOException;
import java.net.URI;
import java.net.http.HttpClient;
import java.net.http.HttpRequest;
import java.net.http.HttpResponse;

public class Gemini {

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

        String apiKey = System.getenv("GEMINI_API_KEY");
        String uri = "https://generativelanguage.googleapis.com/v1beta/openai/chat/completions";

        String requestBody = """
        {
          "model": "gemini-2.5-flash",
          "messages": [
            {
              "role": "system",
              "content": "You are a movie review expert"
            },
            {
              "role": "user",
              "content": "name one movie for software engineers apart from social network, just the name"
            }
          ]
        }
        """;

        HttpClient client = HttpClient.newHttpClient();

        HttpRequest request = HttpRequest.newBuilder()
                .uri(URI.create(uri))
                .header("Content-Type", "application/json")
                .header("Authorization", "Bearer " + apiKey)
                .POST(HttpRequest.BodyPublishers.ofString(requestBody))
                .build();

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

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

OpenAI Code

package com.telusko;

import java.io.IOException;
import java.net.URI;
import java.net.http.HttpClient;
import java.net.http.HttpRequest;
import java.net.http.HttpResponse;

public class OpenAI {

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

        String apiKey = System.getenv("OPENAI_API_KEY");
        String uri = "https://api.openai.com/v1/chat/completions";

        String requestBody = """
        {
          "model": "gpt-4o",
          "messages": [
            {
              "role": "system",
              "content": "You are a movie review expert"
            },
            {
              "role": "user",
              "content": "name one movie for software engineers apart from social network, just the name"
            }
          ]
        }
        """;

        HttpClient client = HttpClient.newHttpClient();

        HttpRequest request = HttpRequest.newBuilder()
                .uri(URI.create(uri))
                .header("Content-Type", "application/json")
                .header("Authorization", "Bearer " + apiKey)
                .POST(HttpRequest.BodyPublishers.ofString(requestBody))
                .build();

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

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

Reading API Keys and Setting API Endpoints

OpenAI reads the API key using System.getenv("OPENAI_API_KEY").
Gemini reads the API key using System.getenv("GEMINI_API_KEY").
OpenAI API endpoint used: Open AI
Gemini API endpoint used: Gemini AI

Defining the JSON Request Body

Both programs define the request body using Java text blocks (""" ... """).
OpenAI request sets the model as "gpt-4o".
Gemini request sets the model as "gemini-2.5-flash".
Both requests send the same messages array:
- A system role for instructions
- A user role asking for a movie name for software engineers

Configuring the HTTP Request

An HttpClient instance is created using HttpClient.newHttpClient().
The HttpRequest is built using HttpRequest.newBuilder().
The URI is set using URI.create(uri).
Both requests set the following headers:
- Content-Type: application/json
- Authorization: Bearer <apiKey>
The request body is attached using:
- HttpRequest.BodyPublishers.ofString(requestBody)
The HTTP method used is POST.

Sending the Request and Handling the Response

The request is sent using:
- client.send(request, HttpResponse.BodyHandlers.ofString())
The response type is HttpResponse<String>.
The response body is printed using:
- System.out.println(response.body())
This prints the raw JSON response returned by OpenAI or Gemini for the given prompt.

First Code

Java Program Structure for OpenAI and Gemini

Gemini Code

OpenAI Code

Reading API Keys and Setting API Endpoints

Defining the JSON Request Body

Configuring the HTTP Request

Sending the Request and Handling the Response

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