将散列键中的日期条目排序 [英] Sort keys which are date entries in a hashmap
问题描述
我有一个hashMap,它有以下值作为键值(sql date,integer)
对:
I have a hashMap which has the following values as key value(sql date , integer)
pairs:
a.put("31-05-2011",67);
a.put("01-06-2011",89);
a.put("10-06-2011",56);
a.put("25-05-2011",34);
当我尝试使用以下命令对基于键的hashMap进行排序:
Map modified_a = new TreeMap中的(a);
并显示它的密钥,如下所示:
when i try to sort the hashMap based on the keys using : Map modified_a=new TreeMap(a); and display the keys it is as follows :
01-06-2011,10-06-2011,25-05-2011, 31-05-2011
但我希望按键排序为 p>
but I want the keys to be sorted as
31-05-2011,25-05-2011,01-06-2011 ,10-06-2011
我可以看到这些值是根据前两位数字(这是日期值)排序的,但我需要月份值也要先考虑和排序,然后每月对相应的日期进行排序。
任何线索??
I can see that the values are being sorted based on the first 2 digits( which is the date value) but I need the month value to also be considered and sort based on months first and then for each month sort the corresponding days. Any clues ??
推荐答案
您可以像
Map<Date, Integer> m = new HashMap<Date, Integer>();
DateFormat dateFormat = new SimpleDateFormat("dd-MM-yyyy");
m.put(new java.sql.Date(dateFormat.parse("31-05-2011").getTime()),67);
m.put(new java.sql.Date(dateFormat.parse("01-06-2011").getTime()),89);
m.put(new java.sql.Date(dateFormat.parse("10-06-2011").getTime()),56);
m.put(new java.sql.Date(dateFormat.parse("25-05-2011").getTime()),34);
Map<Date, Integer> m1 = new TreeMap(m);
DateFormat df = new SimpleDateFormat("dd/MM/yyyy");
for (Map.Entry<Date, Integer> entry : m1.entrySet())
{
System.out.println(df.format(entry.getKey()));
}
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