实现 groovy(java) 的groupBy探索和 groupBy 2次

@Test
    void testBytetoString() {
        def errorCodeList = [
                [code: "1", language: "2", content: "3"],
                [code: "1", language: "2", content: "4"],
                [code: "1", language: "3", content: "5"],
                [code: "1", language: "3", content: "6"],
                [code: "2", language: "1", content: "3"],
                [code: "2", language: "2", content: "3"],
                [code: "1", language: "2", content: "4"]
        ]

• 多次groupBy

def b =  errorCodeList.groupBy {
            it.code
        }.collectEntries {k, v ->
            [(k): v.groupBy {
                it.language
            }.collectEntries {k2, v2 ->
                [(k2): v2.collect {
                    it.content
                }]
            }]
        }
        println b

• 自己实现 groupByKey

def a = groupByKey(errorCodeList, "code").collectEntries { k, v ->
            def tmpv = groupByKey(v, "language").collectEntries { k2, v2 ->
                [(k2): v2.collect {
                    it["content"]
                }]
            }
            [(k): tmpv]
        }
        println a
  static HashMap<String, List> groupByKey(List<Map> list, String field) {

        HashMap store = new HashMap<String, List>()

        for(Map map : list) {
            String key = map[field]
//            map.remove(field)
            if (store.containsKey(key)) {
                store.replace(key, store.get(key) + map)
            } else {
                store.put(key, [map])
            }
        }
        store
    }

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