java - 想要从日期数组中计算一个月的条目数

Question

我有一个包含以下类型条目的日期数组..

2012-03-20 13:50:27.278
2011-08-11 00:30:31.121
2011-08-11 00:35:48.726
2011-08-11 01:18:41.712
2011-08-11 01:20:20.403
2011-08-11 01:22:49.588
2011-08-11 01:25:51.451
2013-02-14 19:39:06.837
2011-08-11 14:46:01.376
2011-08-13 05:43:20.744
2011-08-13 05:46:05.477
2011-08-16 08:07:56.551
2011-08-18 13:21:55.534
2011-08-18 13:23:13.961
2011-08-18 13:33:58.683
2011-08-18 13:36:29.199
2011-08-23 12:02:36.086
2012-12-31 13:49:21.999
2013-02-28 17:49:18.938
2013-05-04 19:17:39.512
2011-09-02 20:17:33.023
2011-09-05 21:50:18.495
2011-09-09 21:14:26
2011-09-09 21:42:48.984
2011-09-09 21:59:27.321

我想计算每个月的整体数量？？

Answer 1

你可以试试这个

    String[] dateArr=new String[10];
    Map<String,Integer> monthCount=new HashMap<>();
   for(String i:dateArr){
      Integer countMonth=monthCount.get(i.split("-")[1]);
      if(countMonth==null){
         countMonth=0;
      }
       monthCount.put(i,countMonth+1);   // here you have number of entries for each month
   }