How to sort data of ArrayList of hashmap on The Basis of Date

Question

i have sorted the data on the basis of name. but when i am going to sort the data of arraylist of hash map on the basis of "date", i have no idea how to solve it. my Method for sort by name is given below.

protected ArrayList<HashMap<String, String>> setListOrderByName(ArrayList<HashMap<String, String>> menuItems2) {

    Collections.sort(menuItems2, new Comparator<HashMap<String, String>>() {
        public int compare(HashMap<String, String> mapping1,
                HashMap<String, String> mapping2) {
            return mapping1.get(KEY_NAME).compareTo(mapping2.get(KEY_NAME));
        }
    });

    return menuItems2;
}

i have receive the data from xml parsing. where we get name, date ,time and etc in string format.

If it is a date stored as string, easiest is to convert string to date and then compare it. — bitkot, Apr 02 '14 at 13:04
@AmitChotaliya Or store it yyyyMMdd so that it sorts lexically. — Elliott Frisch, Apr 02 '14 at 13:05
Here's how to compare date http://stackoverflow.com/questions/2592501/compare-dates-in-java and parse date http://stackoverflow.com/questions/999172/how-to-parse-a-date — bitkot, Apr 02 '14 at 13:06
@ElliottFrisch, yes, storing as a date is even better, but that would effect other code written based on current format. — bitkot, Apr 02 '14 at 13:08

loknath · Accepted Answer · 2014-04-02T13:20:39.397

6

convert string to date and then compare it

  protected ArrayList<HashMap<String, String>>      
setListOrderByName(ArrayList<HashMap<String, String>> menuItems2) {

Collections.sort(menuItems2, new Comparator<HashMap<String, String>>() {
DateFormat f = new SimpleDateFormat("dd/MM/yyyy '@'hh:mm a");//do determ    

@Override
public int compare(HashMap<String, String> mapping1,
    HashMap<String, String> mapping2) {
try {
    return f.parse(mapping1.get(KEY_NAME)).compareTo(f.parse(mapping2.get(KEY_NAME)));
} catch (ParseException e) {
    throw new IllegalArgumentException(e);
}
}
});
return menuItem2;
}

edited Apr 02 '14 at 13:20

answered Apr 02 '14 at 13:09

loknath

1,362
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25

That's a very specific date format. How did you determine it? – Elliott Frisch Apr 02 '14 at 13:10
@ElliottFrisch to determine the String format visit http://stackoverflow.com/questions/7579227/how-to-get-the-given-date-string-formatpattern-in-java – loknath Apr 02 '14 at 13:14

score 2 · Answer 2 · answered Apr 02 '14 at 13:31

Here example for sort HashMap based on string date

    protected ArrayList<HashMap<String, String>> setListOrderByName(ArrayList<HashMap<String, String>> menuItems2) {

        Collections.sort(menuItems2, new Comparator<HashMap<String, String>>() {
            public int compare(HashMap<String, String> mapping1,
                    HashMap<String, String> mapping2) {

                DateFormat formatter = new SimpleDateFormat("yyyy-MM-dd'T'HH:mm:ssz");
                Date date1 = formatter.parse(mapping1.get(DATE));


                DateFormat formatter = new SimpleDateFormat("yyyy-MM-dd'T'HH:mm:ssz");
                Date date2 = formatter.parse(mapping2.get(DATE));

                if(date1.after(date2)){
              return mapping1.get(DATE);
                }else{
                  return mapping2.get(DATE);
                }                           
            }
        });

        return menuItems2;
    }

How to sort data of ArrayList of hashmap on The Basis of Date

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