static RefKind getRefkind(int tag) {
            switch(tag) {
                case 1:
                    return REF_getField;
                case 2:
                    return REF_getStatic;
                case 3:
                    return REF_putField;
                case 4:
                    return REF_putStatic;
                case 5:
                    return REF_invokeVirtual;
                case 6:
                    return REF_invokeStatic;
                case 7:
                    return REF_invokeSpecial;
                case 8:
                    return REF_newInvokeSpecial;
                case 9:
                    return REF_invokeInterface;
                default:
                    return null;
            }
        }