本文介绍了如何使用groovy对列表进行分组的处理方法，对大家解决问题具有一定的参考价值，需要的朋友们下面随着小编来一起学习吧！
问题描述
我有一个列表，我想按照marketName和commodityName分组，列出价格：例如[Terra，Wheat，1000.0] - Terra是市场名称，Wheat是商品名称，1000.0是价格
def marketCommodityGroup = [ [Merkato，Wheat，1000.0]， [Shola，Wheat，1875.0]， [Merkato，Barley ，5000.0]， [Merkato，小麦，1000.0]， [Merkato，小麦，1500.0] ]我希望输出为：
<$ c $ [Merkato：[Wheat：[1000.0,1000.0,1500.0]]]， [Merkato：[Barley：[5000.0]]]， [Shola：[Wheat：[1875.0]]] ]解决方案
好吧，这里有一个方法。
def mapped = marketCommodityGroup.groupBy { [（it [0]）：it [1]] } .collect {k，v - > def grouping = k.find {true} def prices = v.inject（[]）{acc，val - > acc + val [2]} [（grouping.key），[（grouping.value）：prices]] } .sort {left，right - > right [0]< => left [0] } .collect { [（it [0]）：it [1]] }
- 第一个 groupBy 确实 通过市场名称和商品名称
- collect 创建除最终 k：v association：
- grouping 是键映射拆分中的唯一条目，因此可以重新排序到期望的形式
- 价格用非常方便的 inject 来完成，它是Groovy等同于折叠功能语言中的操作
- sort 用于按照指定的顺序翻转订单 - 必须确定实际的逻辑是什么，以便您可以替换它
- last collect 做最终的地图分配以获得确切的想要的表单
是的，它有点密集和神奇的，但你总是可以移动关闭def带有适当的描述性名称。
I have a list of list that I want to group by marketName and commodityName, by listing price: e.g. ["Terra", "Wheat", 1000.0] - "Terra" is Market name, "Wheat" is Commodity Name, 1000.0 is price
def marketCommodityGroup = [ ["Merkato", "Wheat", 1000.0], ["Shola", "Wheat", 1875.0], ["Merkato", "Barley", 5000.0], ["Merkato", "Wheat", 1000.0], ["Merkato", "Wheat", 1500.0] ]I would like the output to be:
[ ["Merkato": ["Wheat" : [1000.0, 1000.0, 1500.0]]], ["Merkato": ["Barley": [5000.0]]], ["Shola": ["Wheat": [1875.0]]] ]解决方案
Alright, here's one way of doing it.
def mapped = marketCommodityGroup.groupBy { [(it[0]) : it[1]] }.collect { k,v -> def grouping = k.find { true } def prices = v.inject([]) { acc,val -> acc + val[2] } [ (grouping.key) , [ (grouping.value) : prices ] ] }.sort { left, right -> right[0] <=> left[0] }.collect { [(it[0]) : it[1] ] }
- first groupBy does exactly what you said, it groups by the market name and commodity name
- collect creates the wanted structure excluding the final k:v association:
- grouping is the only entry in the key map split so that it can be reordered to desired form
- prices is done with the very handy inject which is Groovy's equivalent for the fold left operation in functional languages
- sort is for flipping the order as you specified - had to quess what the actual logic is so you may want to replace it
- last collect does the final map assignment to get the exact wanted form
Yes, it's a bit dense and magical but you can always move the closures to defs with proper, descriptive names.
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