Java根据年度将数据分组
作者:互联网
现在有这么一组数据
code name year
45615654 x1 2018-2019
78912648 x2 2018-2019
42364322 x3 2017-2018
87635225 x4 2016-2017
我想在Java后台将数据按year分组该怎么做呢
首先数据一定是根据year排序好的
最后返到前台的数据格式是这样的
原理就是year每换一次map就往里put一组year和list
chargeList: [ { year: 2018-2019, list: [ { code: 45615654, name: "x1" }, { code: 78912648, name: "x2" }, ] } ]
第一种实现:
想要获得这样的数据需要最外层循环根据不重复year的个数来循环
内层再根据year来判断将什么数据放到list中
最后将year和list装在dataMap里
List<ClientResult> clientMsts = clientMstMapper.selectHeatingData2(); List<Map> dataList = new ArrayList<>(); String year = ""; List<String> yearList = new ArrayList<>(); for (ClientResult c : clientMsts) { if (!year.equals(c.getYear())) { year = c.getYear(); yearList.add(year); } } for (int i = 0; i < yearList.size(); i++) { Map<String, Object> map = new HashMap<>();//装的是code和name Map<String, Object> dataMap = new HashMap<>();//装year和list List<Map> list = new ArrayList<>(); year = yearList.get(i); for (ClientResult c : clientMsts) { if (year.equals(c.getYear())) { map.put("code", c.getCode()); map.put("name", c.getName()); list.add(map); } } dataMap.put("year", year); dataMap.put("list", list); dataList.add(dataMap); } Map<String, Object> map = new HashMap<>(); map.put("dataList", dataList);
第二种实现:
当year不相同的时候往dataMap中put一组数据
List<ClientResult> clientMsts = clientMstMapper.selectHeatingData2(); List<Map> dataList = new ArrayList<>(); String year = ""; List<Map> lists = null; for (ClientResult c : clientMsts) { Map<String, Object> dataMap= new HashMap<>(); boolean a = false; if (!year.equals(c.getClientPaymentYear())) { year = c.getClientPaymentYear(); dataMap.put("year", year); lists = new ArrayList<>(); a = true; } Map map = new HashMap(); map.put("code", c.getClientMstCode()); map.put("name", c.getHousingEstateName()); lists.add(map2); if (a) { dataMap.put("data", lists); dataList.add(map); } } Map<String, Object> map = new HashMap<>(); map.put("dataList", dataList);
这就是Java后台根据年度分组的详细过程,可能还有别的更好地办法,欢迎一起讨论
标签:map,Java,list,put,分组,year,年度,new,dataMap 来源: https://www.cnblogs.com/zouwangblog/p/10984522.html