HTTP/1.1 200 Content-Type:application/json;charset=utf-8 Content-Length:<content data lenght> <content data> 如何用java代码实现这个http请求

可以使用Java中的HttpURLConnection类来实现这个HTTP请求。示例代码如下：

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

public class HttpExample {
    public static void main(String[] args) {
        try {
            URL url = new URL("http://example.com/api");
            HttpURLConnection connection = (HttpURLConnection) url.openConnection();

            // 设置请求方法和请求头
            connection.setRequestMethod("GET");
            connection.setRequestProperty("Content-Type", "application/json;charset=utf-8");

            // 发送请求
            int responseCode = connection.getResponseCode();
            System.out.println("Response Code: " + responseCode);

            // 读取响应
            BufferedReader reader = new BufferedReader(new InputStreamReader(connection.getInputStream()));
            String line;
            StringBuilder response = new StringBuilder();
            while ((line = reader.readLine()) != null) {
                response.append(line);
            }
            reader.close();

            // 输出响应
            System.out.println("Response: " + response.toString());
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
}

其中，url变量为请求的URL地址，connection变量为HttpURLConnection实例，通过设置请求方法和请求头来发送GET请求。最后通过读取响应的方式获取服务器返回的数据。