Connecting URL and posting data to server..

URLConnection.java

public String PostConnection(String value) {
        String response = "";
        HashMap<String, String> datamap = new HashMap<>();
        datamap.put("key", value);
        try {
            response = UrlPostConnection("URL", datamap);
        } catch (IOException e) {
            e.printStackTrace();
        }
        return response;
    }

    public String GetConnection(String value) {
        String response = "";
        try {
            response = UrlGetConnection("URL");
        } catch (IOException e) {
            e.printStackTrace();
        }
        return response;
    }

    private String UrlPostConnection(String Url, HashMap<String, String> datamap) throws IOException {
        String response = "";
        URL url = new URL(Url);
        HttpURLConnection conn = (HttpURLConnection) url.openConnection();
        conn.setReadTimeout(15000);
        conn.setConnectTimeout(15000);
        conn.setRequestMethod("POST");
        conn.setDoInput(true);
        conn.setDoOutput(true);

        OutputStream os = conn.getOutputStream();
        BufferedWriter writer = new BufferedWriter(new OutputStreamWriter(os, "UTF-8"));
        writer.write(getPostDataString(datamap));
        writer.flush();
        writer.close();
        os.close();
        int responseCode=conn.getResponseCode();
        if (responseCode == HttpsURLConnection.HTTP_OK) {
            String line;
            BufferedReader br=new BufferedReader(new InputStreamReader(conn.getInputStream()));
            while ((line=br.readLine()) != null) {
                response+=line;
            }
        }
        else {
            response="";
        }
        return response;
    }

    private String getPostDataString(HashMap<String, String> params) throws UnsupportedEncodingException {
        StringBuilder result = new StringBuilder();
        boolean first = true;
        for(Map.Entry<String, String> entry : params.entrySet()){
            if (first)
                first = false;
            else
                result.append("&");

            result.append(URLEncoder.encode(entry.getKey(), "UTF-8"));
            result.append("=");
            result.append(URLEncoder.encode(entry.getValue(), "UTF-8"));
        }

        return result.toString();
    }

    private String UrlGetConnection(String Url) throws IOException {
        String response = "";
        URL url = new URL(Get_Url);
        HttpURLConnection conn = (HttpURLConnection) url.openConnection();
        conn.setReadTimeout(15000);
        conn.setConnectTimeout(15000);
        int responseCode=conn.getResponseCode();
        if (responseCode == HttpsURLConnection.HTTP_OK) {
            String line;
            BufferedReader br=new BufferedReader(new InputStreamReader(conn.getInputStream()));
            while ((line=br.readLine()) != null) {
                response+=line;
            }
        }
        else {
            response="";
        }
        return response;
    }