我如何在Java8中使用Lambda表達式編寫以下代碼。我是Java 8的新手。for (GlobalPricingRequest globalPricingRequest : globalPricingRequests) { BigDecimal feePerTrans = globalPricingRequest.getFeePerTransact(); if (feePerTrans != null && feePerTrans.intValue() < 0) { throw ExceptionHelper.badRequest("Fee Per Transaction can't be less than zero"); } List<EventTypePricingMapping> eventTypePricingMappings = globalPricingRequest.getEventTypePricingList(); for (EventTypePricingMapping eventTypePricingMapping : eventTypePricingMappings) { BigDecimal feePerRevenue = eventTypePricingMapping.getFeePerRevenue(); if (feePerRevenue != null && feePerRevenue.intValue() < 0) { throw ExceptionHelper.badRequest("Fee Per Transaction can't be less than zero"); } if (eventTypePricingMapping.getFeePerRevenue().intValue() < 0) { throw ExceptionHelper.badRequest("Fee Per Transaction can't be less than zero"); } }}我已經按照建議嘗試了以下代碼。我們還有什么可以改進的代碼，可以使用lambdas編寫更多代碼。globalPricingRequests.forEach((globalPricingRequest) -> { if (checkIfValueLessThanZero(globalPricingRequest.getFeePerTransact())) { throw ExceptionHelper.badRequest("Fee Per Transaction can't be less than zero"); } List<EventTypePricingMapping> eventTypePricingMappings = globalPricingRequest.getEventTypePricingList(); eventTypePricingMappings.forEach((eventTypePricingMapping) -> { if (checkIfValueLessThanZero(eventTypePricingMapping.getFeePerRevenue())) { throw ExceptionHelper.badRequest("Fee Per Transaction can't be less than zero"); } if (checkIfValueLessThanZero(eventTypePricingMapping.getFeePerReg())) { throw ExceptionHelper.badRequest("Fee Per Transaction can't be less than zero"); } });});private boolean checkIfValueLessThanZero(Object object) { if (object instanceof BigDecimal) { if (object != null && ((BigDecimal) object).intValue() < 0) { return true; } } return false;}
3 回答
犯罪嫌疑人X
TA貢獻2080條經驗 獲得超4個贊
通過命令式方法，您正在執行的這種類型的驗證會更好，但是我們可以在適當的地方使用lambda。
首先，我將signum在帖子中使用@ThomasKl?ger的建議，將重復條件與本地謂詞隔離開，因為在這種特定情況下，該條件比更為合適intValue。
Predicate<BigDecimal> criteria = b -> b != null && b.signum() < 0;
那么您的命令式方法將如下所示：
for (GlobalPricingRequest globalPricingRequest : globalPricingRequests) {
isValidOrElseThrowBadRequestException(globalPricingRequest.getFeePerTransact(), criteria);
for (EventTypePricingMapping eventTypePricingMapping : globalPricingRequest.getEventTypePricingList()) {
isValidOrElseThrowBadRequestException(eventTypePricingMapping.getFeePerRevenue(), criteria);
}
}
其中isValidOrElseThrow定義為：
public static void isValidOrElseThrowBadRequestException(BigDecimal data, Predicate<BigDecimal> criteria) throws Exception { // change the exception to the specific one you're using
if(criteria.test(data)) throw ExceptionHelper.badRequest("Fee Per Transaction can't be less than zero");
}
只需在此處和此處進行一些隔離，就可以使代碼更具可讀性。
慕神8447489
TA貢獻1780條經驗 獲得超1個贊
您可以使用流兩次，并提高代碼的可讀性，如下所示：
Predicate<BigDecimal> feeCheck =
feePerTransactOrRevenue -> feePerTransactOrRevenue != null
&& feePerTransactOrRevenue.intValue() < 0;
boolean globalRequestCheck = globalPricingRequests.stream()
.map(GlobalPricingRequest::getFeePerTransact)
.anyMatch(feeCheck);
boolean eventTypeCheck = globalPricingRequests.stream()
.map(GlobalPricingRequest::getEventTypePricingList)
.flatMap(List::stream)
.map(EventTypePricingMapping::getFeePerRevenue)
.anyMatch(feeCheck);
// if any of the element matches the condition, throw the exception
if (globalRequestCheck || eventTypeCheck) {
throw ExceptionHelper.badRequest("Fee Per Transaction can't be less than zero");
}
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