JAVA lambda分组

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}]