如何用Java实现简单的HTTP GET/POST请求？

在Java中，我们可以使用java.net包下的HttpURLConnection或者更现代的Apache HttpClient库来发送HTTP GET和POST请求。这里我将提供一个基本的使用HttpURLConnection的例子：

**GET请求:**

import java.io.BufferedReader;
import java.io.InputStreamReader;
import java.net.HttpURLConnection;
import java.net.URL;

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

        // 设置请求方法
        con.setRequestMethod("GET");

        int responseCode = con.getResponseCode();
        System.out.println("Response Code : " + responseCode);

        BufferedReader in = new BufferedReader(
                new InputStreamReader(con.getInputStream()));
        String inputLine;
        StringBuffer response = new StringBuffer();

        while ((inputLine = in.readLine()) != null) {
            response.append(inputLine);
        }
        in.close();

        // 打印结果
        System.out.println(response.toString());
    }
}

**POST请求:**

import java.io.OutputStream;
import java.io.IOException;

public class SimpleHttpPostRequest {
    public static void main(String[] args) throws IOException {
        String url = "http://example.com/api/resource";
        String postData = "param1=value1&param2=value2"; // 你的数据

        URL obj = new URL(url);
        HttpURLConnection con = (HttpURLConnection) obj.openConnection();
        con.setRequestMethod("POST");
        con.setDoOutput(true); // 告诉服务器我们有数据需要写入

        try(OutputStream os = con.getOutputStream()) {
            byte[] bytes = postData.getBytes("UTF-8");
            os.write(bytes, 0, bytes.length);
        }

        int responseCode = con.getResponseCode();
        System.out.println("Response Code : " + responseCode);
    }
}

记得替换上述代码中的URL为实际的目标地址，并处理可能的异常。