public T registerConverter(Converter<?> converter) {
        if (parameter().getCustomConverterList() == null) {
            parameter().setCustomConverterList(ListUtils.newArrayList());
        }
        parameter().getCustomConverterList().add(converter);
        return self();
    }
Custom type conversions override the default.

@param converter
@return
fastexcel-core/src/main/java/cn/idev/excel/metadata/AbstractParameterBuilder.java