com.dropbox.core.DbxException$BadRequest: {"error_description": "code doesn't exist or has expired", "error": "invalid_grant"}

I uploaded successfully few files using the Dropbox API. But now I am receiving this message:

com.dropbox.core.DbxException$BadRequest: {"error_description": "code doesn't exist or has expired", "error": "invalid_grant"}

for this code

  final String APP_KEY = "aaaaaaaaaaaaaaaa";
  final String APP_SECRET = "sssssssssssssss";

  DbxAppInfo appInfo = new DbxAppInfo(APP_KEY, APP_SECRET);

  DbxRequestConfig config = new DbxRequestConfig("JavaTutorial/1.0",
              Locale.getDefault().toString());
  DbxWebAuthNoRedirect webAuth = new DbxWebAuthNoRedirect(config, appInfo);
  // Have the user sign in and authorize your app.
  String authorizeUrl = webAuth.start();
  System.out.println("1. Go to: " + authorizeUrl);
  System.out.println("2. Click \"Allow\" (you might have to log in first)");
  System.out.println("3. Copy the authorization code.");
  String code = "codexxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx";


  // Once the user has delivered the authorization code to our app, we can
  // exchange that code for an access token via finish:
  DbxAuthFinish authFinish = webAuth.finish(code);
  String accessToken = authFinish.accessToken;

  DbxClient client = new DbxClient(config, accessToken);
  System.out.println("Linked account: "
              + client.getAccountInfo().displayName);