How to Sort an Arraylist of Date in ascending and descending order which is in String format

Question

I have arrayLists of Dates which is in String format then how can I sort this arraylists,

ArrayList<String> aryBeginDate;
ArrayList<String> aryDueDate;

for (int i = 0; i < arySubject.size(); i++) {

    RowItem row = new RowItem();
    row.setSubject(arySubject.get(i).toString());
    row.setUser(aryFromUser.get(i).toString());

    if (aryBeginDate.equals(" ")) {
        row.setStartDate(" ");
    } else {
        row.setStartDate(aryBeginDate.get(i).toString()); \\Have to sort at this line
    }

    if (aryDueDate.equals(" ")) {
        row.setEndDate(" ");
    } else {
        row.setEndDate(aryDueDate.get(i).toString()); \\Have to sort at this line
    }

    aryListBean.add(row);

}

http://stackoverflow.com/questions/13120316/how-to-sort-date-in-descending-order-from-arraylist-date-in-android?rq=1 — Ajay, Feb 26 '13 at 09:42

score 12 · Accepted Answer · answered Feb 26 '13 at 09:43

12

Don't use a String when you want a Date. Use a Date. You should only transfom the Date to a String when displaying it. Otherwise, everywhere in the code, the date should of type Date. This is what allows sorting in chronological order, because dates have a natural order which is chronological.

So, once the RowItem has a startDate and an endDate, both being of type Date, you can sort a list of row items by start date using a simple comparator:

Collections.sort(rowItems, new Comparator<RowItem>() {
    @Override
    public int compare(RowItem r1, RowItem 2) {
        return r1.getStartDate().compareTo(r2.getStartDate());
    }
});

Also, fix your indentationof if/else blocks, because your way is really not readable:

if (aryBeginDate.equals(" ")) {
    row.setStartDate(" ");
} 
else {
    row.setStartDate(aryBeginDate.get(i).toString());
}

answered Feb 26 '13 at 09:43

JB Nizet

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Hello... and what should we do If two dates are same :) – Mit Bhatt Feb 26 '13 at 12:26
Then the compareTo method will return 0, and the order of these two row items is undefined. If you want it defined, then compare the two objects based on another criterion if the first comparison returns 0. – JB Nizet Feb 26 '13 at 12:27
What if I what the latest date first ? – Chetan Gaikwad Jul 12 '15 at 13:33
1

@Chetu you would use `r2.getStartDate().compareTo(r1.getStartDate())`, or `-r1.getStartDate().compareTo(r2.getStartDate())`. – JB Nizet Jul 12 '15 at 15:29
_As a side note_: it would be better to also check if any of the dates is `null`, otherwise one can easily get _NPE_. – informatik01 Oct 16 '15 at 15:52

score 4 · Answer 2 · answered Feb 11 '14 at 05:36

Very Simple Answer:For Ascending just call this method:

Collections.sort(mArrayList, new OutcomeAscComparator());
public class OutcomeAscComparator implements Comparator<Select>
    {
        public int compare(Select left, Select right) {
            return left.getOutcome().compareTo(right.getOutcome());
        }
    }

Select is my model, For Descending:

Collections.sort(mArrayList, new OutcomeDescComparator());
public class OutcomeDescComparator implements Comparator<Select>
    {
        public int compare(Select left, Select right) {
            return right.getOutcome().compareTo(left.getOutcome());
        }
    }

Please dont forget to refresh your list view IF you want your list to be AScending and Descending

                mListView.invalidateViews();

                mAdapter.notifyDataSetChanged();

score 1 · Answer 3 · answered Feb 26 '13 at 09:39

1

This will be very painful if you try to sort this yourself with Strings. I'd recommend you to parse the String to a Date (check JodaTime for a very convenient Date/Time tool) and then sort with java.util.Collections.sort().

answered Feb 26 '13 at 09:39

fweigl

21,278
20
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1

I am already feeling pain :) I have to change so much things to parse String to Date..plz Help me..I have stuck in my Project – Mit Bhatt Feb 26 '13 at 09:43

score 1 · Answer 4 · answered Feb 26 '13 at 09:48

You can use a Comparator to sort the list. Something like this:

Collections.sort(aryListBean, new Comparator<RowItem>() {
    @Override
    public int compare(RowItem r1, RowItem r2) {
        // Place your compare logic here
    }
});

score 0 · Answer 5 · answered Feb 26 '13 at 09:37

0

There is an in built function on ArrayList sort(). Since you are using String, this will work.

answered Feb 26 '13 at 09:37

Aashray

2,753
16
22

But it'll just sort the Strings per Alphabet, not the Dates, and I guess he wants to sort the dates. – fweigl Feb 26 '13 at 09:53
Numbers are also considered in the same way as strings. 1 will always come before 2 when you sort them as strings. – Aashray Feb 26 '13 at 09:56
can you give me an example plz?? – Mit Bhatt Feb 26 '13 at 10:39
First comment `Collections.sort(arr);` and run, then uncomment and run. You will see the difference:`public static void main(String[] args) { ArrayList arr=new ArrayList(); arr.add("12-12-12"); arr.add("11-12-12"); arr.add("09-12-12"); Collections.sort(arr); System.out.println(arr); }` – Aashray Feb 26 '13 at 11:41

score 0 · Answer 6 · answered Feb 26 '13 at 09:42

0

First convert the String in Date and create the arraylist. Then use the Collection sort method for sorting the arraylist.

answered Feb 26 '13 at 09:42

Ranu Jain

577
4
11

How to Sort an Arraylist of Date in ascending and descending order which is in String format

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