原始碼取自某簡訊平臺，不依賴第三方庫，無異常處理程式碼，僅供參考

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.PrintWriter;
import java.net.URL;
import java.net.URLConnection;

public class HttpRequest {
    /**
     * 向指定 URL 傳送POST方法的請求
     * 
     * @param url
     *            傳送請求的 URL
     * @return 所代表遠端資源的響應結果
     */
 

    public static String sendPost(String url, String param) {
        PrintWriter out = null;
        BufferedReader in = null;
        String result = "";
        try {
            URL realUrl = new URL(url);
            // 開啟和URL之間的連線
            URLConnection conn = realUrl.openConnection();
            // 設定通用的請求屬性
 

            conn.setRequestProperty("accept", "*/*");
            conn.setRequestProperty("connection", "Keep-Alive");
            conn.setRequestProperty("user-agent",
                    "Mozilla/4.0 (compatible; MSIE 6.0; Windows NT 5.1;SV1)");
            // 傳送POST請求必須設定如下兩行
            conn.setDoOutput
 
(true);
            conn.setDoInput(true);
            // 獲取URLConnection物件對應的輸出流
            out = new PrintWriter(conn.getOutputStream());
            // 傳送請求引數
            out.print(param);
            // flush輸出流的緩衝
            out.flush();
            // 定義BufferedReader輸入流來讀取URL的響應
            in = new BufferedReader(
                    new InputStreamReader(conn.getInputStream()));
            String line;
            while ((line = in.readLine()) != null) {
                result += line;
            }
        } catch (Exception e) {
            System.out.println("傳送 POST 請求出現異常！"+e);
            e.printStackTrace();
        }
        //使用finally塊來關閉輸出流、輸入流
        finally{
            try{
                if(out!=null){
                    out.close();
                }
                if(in!=null){
                    in.close();
                }
            }
            catch(IOException ex){
                ex.printStackTrace();
            }
        }
        return result;
    }    
}

測試一下：

System.out.println(HttpRequest.sendPost("http://httpbin.org/post", "abc"));

返回值：

{
    "args": { }, 
    "data": "", 
    "files": { }, 
    "form": {
        "abc": ""
    }, 
    "headers": {
        "Accept": "*/*", 
        "Connection": "close", 
        "Content-Length": "3", 
        "Content-Type": "application/x-www-form-urlencoded", 
        "Host": "httpbin.org", 
        "User-Agent": "Mozilla/4.0 (compatible; MSIE 6.0; Windows NT 5.1;SV1)"
    }, 
    "json": null, 
    "origin": "111.11.1.111", 
    "url": "http://httpbin.org/post"
}

測試成功！