Here are some examples of using URLConnection and HttpURLConnection in Java:

Example 1: Reading data from a URL using URLConnection

import java.net.*;
import java.io.*;

public class URLConnectionExample {
    public static void main(String[] args) throws Exception {
        URL url = new URL("https://www.example.com");
        URLConnection con = url.openConnection();

        BufferedReader in = new BufferedReader(new InputStreamReader(con.getInputStream()));
        String inputLine;
        while ((inputLine = in.readLine()) != null) {
            System.out.println(inputLine);
        }
        in.close();
    }
}

This example reads data from a URL using URLConnection and prints it to the console.

Example 2: Posting data to a URL using HttpURLConnection

import java.net.*;
import java.io.*;

public class HttpURLConnectionExample {
    public static void main(String[] args) throws Exception {
        String url = "https://www.example.com/api/endpoint";
        URL obj = new URL(url);
        HttpURLConnection con = (HttpURLConnection) obj.openConnection();

        // Set the request method to POST
        con.setRequestMethod("POST");

        // Set the request headers
        con.setRequestProperty("Content-Type", "application/json");

        // Set the request body
        String requestBody = "{\"name\": \"John Doe\", \"email\": \"[email protected]\"}";
        con.setDoOutput(true);
        OutputStream os = con.getOutputStream();
        os.write(requestBody.getBytes());
        os.flush();
        os.close();

        // Get the response code and response message
        int responseCode = con.getResponseCode();
        String responseMessage = con.getResponseMessage();
        System.out.println("Response code: " + responseCode);
        System.out.println("Response message: " + responseMessage);

        // Read the response body
        BufferedReader in = new BufferedReader(new InputStreamReader(con.getInputStream()));
        String inputLine;
        StringBuffer response = new StringBuffer();
        while ((inputLine = in.readLine()) != null) {
            response.append(inputLine);
        }
        in.close();

        // Print the response body
        System.out.println(response.toString());
    }
}

This example posts data to a URL using HttpURLConnection. It sets the request method to POST, adds a Content-Type header to indicate that the request body is in JSON format, sets the request body, and then reads the response body and prints it to the console.