code: public static AccessToken createFromExistingAccessToken(String accessToken, Date expirationTime,
              Date lastRefreshTime, AccessTokenSource accessTokenSource, List<String> permissions) {
          if (expirationTime == null) {
              expirationTime = DEFAULT_EXPIRATION_TIME;
          }
          if (lastRefreshTime == null) {
              lastRefreshTime = DEFAULT_LAST_REFRESH_TIME;
          }
          if (accessTokenSource == null) {
              accessTokenSource = DEFAULT_ACCESS_TOKEN_SOURCE;
          }
  
          return new AccessToken(accessToken, expirationTime, permissions, null, accessTokenSource, lastRefreshTime);
      }
docs: Creates a new AccessToken using the supplied information from a previously-obtained access
  token (for instance, from an already-cached access token obtained prior to integration with the
  Facebook SDK).
  
  @param accessToken       the access token string obtained from Facebook
  @param expirationTime    the expiration date associated with the token; if null, an infinite expiration time is
  assumed (but will become correct when the token is refreshed)
  @param lastRefreshTime   the last time the token was refreshed (or when it was first obtained); if null,
  the current time is used.
  @param accessTokenSource an enum indicating how the token was originally obtained (in most cases,
  this will be either AccessTokenSource.FACEBOOK_APPLICATION or
  AccessTokenSource.WEB_VIEW); if null, FACEBOOK_APPLICATION is assumed.
  @param permissions       the permissions that were requested when the token was obtained (or when
  it was last reauthorized); may be null if permission set is unknown
  @return a new AccessToken