android - How to resolve Attempt to invoke virtual method 'boolean java.lang.String.equalsIgnoreCase(java.lang.String)?

I have an app in which i am getting error "Attempt to
invoke virtual method 'boolean java.lang.String.equalsIgnoreCase(java.lang.String)"
please explain meaning and solution for
that

code:-

            String receivedResult = parseJsonResultSetFav(result);
 if
            (receivedResult.equalsIgnoreCase("SUCCESS")) {
 CustomerTicketDialogClass ctdc
            = new CustomerTicketDialogClass(getActivity(),
 "successful", "successfully
            sent mail to your email id ", "ViewDetails");
 ctdc.show();

            ctdc.setCanceledOnTouchOutside(false);
 } else {

            CustomerTicketDialogClass ctdc = new
            CustomerTicketDialogClass(getActivity(),

 "failure",
            receivedResult, "ViewDetails");
 ctdc.show();

            ctdc.setCanceledOnTouchOutside(false);

            }