Not able to generate access Token

Not able to generate access Token

Hi,
 I have followed below guide to connect to Zoho CRM using Java

https://help.zoho.com/portal/kb/articles/java-sdk-create-first-app

When i ran application to get access token and refresh token getting below error : 

 com.zoho.oauth.common.ZohoHTTPConnector post
INFO: STATUS_CODE = 400 ,RESPONSE_JSON = <!DOCTYPE html><html><head><meta http-equiv="X-UA-Compatible" content="IE=edge"><title>Server error occurred</title><style>    body { margin:0px; padding:0px;font-family:"Open sans";font-weight: 300; }    .zohologo {background: transparent url(' https://img.zohostatic.com/iam/m4007.98/images/rebrand.gif') no-repeat -9px -199px;width: 210px;height: 29px;margin: 4px 0px 0px 6px; border: none;}     .errmaindiv {text-align: center;}    .errmsgdiv {margin-top:5px; border:6px solid #BFCAFF;}    .errtxtheader b {float:left; font-size:15px; margin:0px; padding:15px 0px 0px 5px;}    .err-reason {font-size:13px;}    .abusetxt {padding: 5px 0px 5px 5px; font-size: 13px; text-align: center; font-weight: 300; margin-top: 20px;}    .abusetxt a {color:#085DDC; text-decoration:none;}    .abusetxt a:hover {text-decoration:underline;}    .logo-top {background-image: url(' https://img.zohostatic.com/iam/m4007.98/images/zlogo.png');    width: 100px;  height: 35px;  margin: 40px auto;  background-repeat: no-repeat;}    .title1{margin-top:-14px;font-size:30px;font-family: "Open sans";font-weight:300;text-align: center;} .title2 {font-size:18px;width: 500px;margin-bottom: 10px;margin-top: 10px;} .bdre2 { border-bottom: 2px solid #000; height: 1px; margin: 6px auto; width: 100px; } .errorLogo{background: url(" https://img.zohostatic.com/iam/m4007.98/images/unauthsprite.png") no-repeat scroll 5px 10px transparent; height: 130px; width: 150px;}  .error-reason{font-size: 13px; line-height: 22px; margin-top: 13px;font-weight: 300} @font-face {    font-family: 'Open Sans'; font-weight: 400; font-style: normal; src :local('Open Sans'),url(' https://img.zohostatic.com/iam/m4007.98/images/opensans/font.woff') format('woff');   } </style></head><body>    <table class="errtbl" align="center" cellpadding="0" cellspacing="0">     <div class="logo-top"></div> <div class="title1">Uh, oh!</div> <div class="bdre2"></div> <tr><td  valign="middle">     <div class="errmaindiv">     <div class="errorLogo" style=" margin-left: 180px; margin-top: 11px; "></div> <div>     <div style="font-size: 16px; font-weight: 500;">     Server error occurred     </div>     <div class="error-reason">     <div> Looks like you typed an incorrect address</div>     <div> Or</div>     <div> the URL you clicked is invalid.</div>         </div> </div>     </div> </td></tr> <tr><td  valign="middle">     <div class="abusetxt">If you still feel the URL is correct, please send us a mail to <a href="mailto: support@zohoaccounts.com"> support@zohoaccounts.com</a></div> </td></tr>    </table></body></html>
Exception in thread "main" com.zoho.oauth.common.ZohoOAuthException. Caused by : org.json.JSONException: A JSONObject text must begin with '{' at 1 [character 2 line 1]
at com.zoho.oauth.client.ZohoOAuthClient.generateAccessToken(ZohoOAuthClient.java:101)
at com.example.zoho.demo.resources.InitOauth.generateToken(InitOauth.java:16)
at com.example.zoho.demo.resources.InitOauth.main(InitOauth.java:10)