java - Groovy中的GroupBy

我想通过其ProductType及其相应的分组对订阅详细信息进行分组List<Long> planReferenceIds
密钥:planSubscription.productSubscription.productType
值:planSubscription.planReferenceId
我似乎不知道如何以“常规方式”执行此操作

private static Map<ProductType, List<Long>> buildPlanSubscriptionDetails(List<PlanSubscription> planSubscriptions) {
        Map<ProductType, List<Long>> subscriptionDetails = [:]

        subscriptionDetails = planSubscriptions.groupBy({it.productSubscription.productType })

        return subscriptionDetails

编辑:

这是我想出的，但我猜不是它的Groovy方式

planSubscriptions.each { PlanSubscription planSubscription ->
            List<Long> planRefIds = subscriptionDetails.get(planSubscription.productSubscription.productType)

            if (planRefIds) {
                planRefIds.add(planSubscription.planReferenceId)
            } else {
                subscriptionDetails.put(planSubscription.productSubscription.productType, [planSubscription.planReferenceId] as List)
            }
        }

先感谢您!

最佳答案

分组后应使用collectEntries:

Map<ProductType, List<Long>> result = subscriptionDetails
        .groupBy { it.productSubscription.productType }
        .collectEntries { pt, sd ->  [pt, sd*.planReferenceId]}