JAVA lambda分组

?

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38

public static void main(String[] args) {           List<Map<String,Object>> list = new ArrayList<>();           Map<String,Object> map1 = new HashMap<String, Object>();         map1.put("stockCode","000001.SZ");         map1.put("stockName","平安银行");         map1.put("traddate","2023-06-07");           Map<String,Object> map2 = new HashMap<String, Object>();         map2.put("stockCode","000002.SZ");         map2.put("stockName","万科A");         map2.put("traddate","2023-06-07");           Map<String,Object> map3 = new HashMap<String, Object>();         map3.put("stockCode","000002.SZ");         map3.put("stockName","万科A");         map3.put("traddate","2023-06-08");           list.add(map1);         list.add(map2);         list.add(map3);           //通过股票去重该list中某个key并存储到list中         List<Object> distinctStockList = list.stream().map(m -> m.get("stockCode")).distinct().collect(Collectors.toList());           System.err.println("去重后股票列表为===" + distinctStockList.toString());           //通过股票分组该list         Map<Object, List<Map<String, Object>>> stockCollect = list.stream().collect(Collectors.groupingBy(m -> m.get("stockCode")));           for (int i = 0; i < distinctStockList.size(); i++) {               List<Map<String, Object>> listByStock = stockCollect.get(distinctStockList.get(i));             System.err.println("根据单个股票输出===" + listByStock.toString());           }     }

　　打印输出为：

去重后股票列表为===[000001.SZ, 000002.SZ]
根据单个股票输出===[{stockName=平安银行, traddate=2023-06-07, stockCode=000001.SZ}]
根据单个股票输出===[{stockName=万科A, traddate=2023-06-07, stockCode=000002.SZ}, {stockName=万科A, traddate=2023-06-08, stockCode=000002.SZ}]