Explain the differences between HTTP GET and POST methods and their usage scenarios.

HTTP GET and POST methods differ in purpose and data transmission method:

• GET is used to retrieve data from the server. Parameters are passed in the URL (query string), which limits the amount of data and makes requests cacheable and bookmarkable. GET requests should be idempotent (not change the server state).

• POST is used to send data to the server, for example, when creating or updating resources. Data is sent in the request body, allowing larger volumes and more sensitive information to be transmitted. POST requests are not cached and are not stored in browser history.

When to use:

• GET — for requests that do not change data (e.g., retrieving a list of users).
• POST — for operations that change the server state (e.g., submitting a registration form).

Example in Java using HttpURLConnection:

URL url = new URL("https://example.com/api/data");
HttpURLConnection con = (HttpURLConnection) url.openConnection();
con.setRequestMethod("GET");
// For POST:
// con.setRequestMethod("POST");
// con.setDoOutput(true);
// try (OutputStream os = con.getOutputStream()) {
//     byte[] input = postData.getBytes("utf-8");
//     os.write(input, 0, input.length);
// }