java - 如何将泛型用于具有不同输入的相同方法

Question

private Set<String> extractOfferKeysForAbstractOffers(List<AbstractOfferDto> selectedOffers) {
        Set<String> offerKeys = new HashSet<String>();
        for (AbstractOfferDto offer : selectedOffers) {
            offerKeys.add(offer.getOfferKey());
        }
        return offerKeys;
    }

 private Set<String> extractOfferKeysForOffers(List<OfferDto> selectedOffers) {
        Set<String> offerKeys = new HashSet<String>();
        for (OfferDto offer : selectedOffers) {
            offerKeys.add(offer.getOfferKey());
        }
        return offerKeys;
    }

我想使用泛型，而不是使用几乎相同的方法只是输入不同。我是这样创建的。

private <T> Set<String> extractOfferKeysForOffers(List<T> offers) {
        Set<String> offerKeys = new HashSet<String>();
        for (T offer : offers) {
            offerKeys.add(offer.getOfferKey());
        }
        return offerKeys;
    }

但问题是 offer.getOfferKey() 无法识别。报价的唯一选项是 AbstractOfferDto 或 OfferDto。

我如何在此示例中使用泛型？

Answer 1

将抽象类型告诉编译器:

private <T extends AbstractOfferDto> Set<String> extractOfferKeysForOffers(List<T> offers) {
        Set<String> offerKeys = new HashSet<String>();
        for (T offer : offers) {
            offerKeys.add(offer.getOfferKey());
        }
        return offerKeys;
    }