Introduction

In today’s fast-paced world, tracking stock prices has become an essential task for investors and traders.
With the rise of financial applications, it’s crucial to get real-time updates on stock prices. This article
guides you on how to track and display stock prices using an API in the Java programming language.

The objective of this project is to demonstrate how to fetch stock price data from a public API and display it
using a simple Java program. We will be using the Alpha Vantage API, which provides free access
to stock data, allowing us to build a basic stock tracker.

Objective

The objective is to create a Java program that retrieves stock prices from an API and displays them in a user-friendly manner.

Code Example

import java.net.HttpURLConnection;
import java.net.URL;
import java.io.BufferedReader;
import java.io.InputStreamReader;
import org.json.JSONObject;

public class StockTracker {

    private static final String API_KEY = "YOUR_API_KEY"; // Replace with your API Key from Alpha Vantage
    private static final String BASE_URL = "https://www.alphavantage.co/query?function=TIME_SERIES_INTRADAY&symbol=";

    public static void main(String[] args) {
        // Example: Get stock data for "AAPL" (Apple Inc.)
        String symbol = "AAPL";
        
        try {
            // Construct the URL with the symbol and API key
            String urlString = BASE_URL + symbol + "&interval=5min&apikey=" + API_KEY;
            URL url = new URL(urlString);
            
            // Send a GET request to the API
            HttpURLConnection connection = (HttpURLConnection) url.openConnection();
            connection.setRequestMethod("GET");
            BufferedReader reader = new BufferedReader(new InputStreamReader(connection.getInputStream()));
            String inputLine;
            StringBuffer response = new StringBuffer();
            
            // Read the response line by line
            while ((inputLine = reader.readLine()) != null) {
                response.append(inputLine);
            }
            reader.close();
            
            // Parse the JSON response
            JSONObject jsonResponse = new JSONObject(response.toString());
            
            // Extract and display the stock data
            JSONObject timeSeries = jsonResponse.getJSONObject("Time Series (5min)");
            String latestTime = timeSeries.keys().next();
            JSONObject latestData = timeSeries.getJSONObject(latestTime);
            String openPrice = latestData.getString("1. open");
            String highPrice = latestData.getString("2. high");
            String lowPrice = latestData.getString("3. low");
            String closePrice = latestData.getString("4. close");
            
            System.out.println("Stock Data for " + symbol + " at " + latestTime);
            System.out.println("Open Price: " + openPrice);
            System.out.println("High Price: " + highPrice);
            System.out.println("Low Price: " + lowPrice);
            System.out.println("Close Price: " + closePrice);
        } catch (Exception e) {
            System.err.println("Error fetching stock data: " + e.getMessage());
        }
    }
}

Explanation of Program Structure

The program consists of a few key components:

• API URL Construction: The program constructs the API URL with a stock symbol (like “AAPL”) and
  the interval (in this case, “5min”) for fetching stock data.
• HttpURLConnection: We use HttpURLConnection to send a GET request to the Alpha Vantage API
  and fetch the response.
• JSON Parsing: The response from the API is in JSON format. We use the JSONObject class
  to parse the data and extract the stock information such as open, high, low, and close prices.
• Error Handling: A try-catch block is used to handle any errors that might occur during the API call
  or while processing the response.

This code is simple and easy to understand, providing a quick way to track stock prices using an API in Java.

How to Run the Program

Follow these steps to run the program:

1. Install Java: Make sure Java is installed on your computer. You can download it from the official Java website.
2. Obtain an API Key: Go to Alpha Vantage and
   sign up for a free API key.
3. Set Up Your Project: Create a new Java project and copy the provided code into a new class file.
4. Replace the API Key: Replace the YOUR_API_KEY placeholder in the code with your actual API key.
5. Run the Program: Compile and run the program. The stock price data for the given symbol will be displayed in the console.

This is a basic implementation, and you can extend it further by adding more features such as tracking multiple stocks,
setting up a graphical user interface (GUI), or scheduling automatic updates.