I have to use Oauth JWT flow to got the access token but while i execute my code then it show me following error,
 

{
     "error" : "invalid_grant",
     "error_description" : "user hasn't approved this consumer"
}

I setup all the related things like create the App and upload the certificate and also create the currect JWT token as per doc Here
and post the following request for access token,
 

HttpPost httpPost = new HttpPost("https://login.salesforce.com/services/oauth2/token");
httpPost.addHeader("Content-Type", "application/x-www-form-urlencoded");
List<NameValuePair> params = new ArrayList<NameValuePair>();
params.add(new BasicNameValuePair("grant_type", "urn:ietf:params:oauth:grant-type:jwt-bearer"));
params.add(new BasicNameValuePair("assertion", clientAssertion));			
httpPost.setEntity(new UrlEncodedFormEntity(params));
HttpResponse response = httpClient.execute(httpPost);

And I also accept the application and related permission by following request,

https://login.salesforce.com/services/oauth2/authorize?client_id=3MVG9ZL0ppGP5UrDITkMBDGuTYGHeynoEt40ZRWCcaYsycFHYDcm2LnqukCNurLNx33LH1c.0rrfG8VrQaqri&redirect_uri=https://localhost/myapp&response_type=code     

I think I done all the things to get the access token but I M GETTING ERROR.
Could you please somebody help me for solving this problem.
Thank You.