CODEWITHSUNDEEP
javaandroidarraylistcollections
Emy Alsabbagh
Emy Alsabbagh

Reputation: 297

Sort ArrayList with times in Java

I have a List<String> that contains a list of times from 8:00 am to 4:00 pm.

When I show it in output it appears unsorted, and when I use Collections.sort(myList); it sorts it as from 1:00 pm to 8:00 am.

How could I sort my list from 8:00am to 4:00pm ?

Upvotes: 3

Views: 7688

Answers (6)

Shaikh Mohib
Shaikh Mohib

Reputation: 288

DetailsVOTemp model has time and add set-get method and I already have a list which is list with name of list.

Get the time and latlong from the list and store in two arraylist than finally sort it 

    List< DetailsVOTemp> firstlist = new ArrayList<>();
    List<DetailsVOTemp> secondlisr = new ArrayList<>();

    for (int i = 0; i < list.size(); i++) {
         DetailsVOTemp mDetailsVOTemp = new  DetailsVOTemp();
        mDetailsVOTemp.setTime(list.get(i).getTime());
        mDetailsVOTemp.setAdd(list.get(i).getLatLong());
        mVoTemps.add(mDetailsVOTemp);
    }
    for (int i = 0; i < list.size(); i++) {
        DetailsVOTemp mDetailsVOTemp = new  DetailsVOTemp();
        mDetailsVOTemp.setTime(list.get(i).getDropOffTime());
        mDetailsVOTemp.setAdd(list.get(i).getDropLatLong());
        mVoTemps1.add(mDetailsVOTemp);
    }

    mVoTemps.addAll(mVoTemps1);
    Collections.sort(mVoTemps, new Comparator<DetailsVOTemp>() {

        @Override
        public int compare(DetailsVOTemp o1, DetailsVOTemp o2) {
            return o1.getTime().compareTo(o2.getTime());
        }
    });

    StringBuilder mBuilder = new StringBuilder();
    StringBuilder mBuilder1 = new StringBuilder();
    for (int i = 0; i < mVoTemps.size(); i++) {
        mBuilder1.append(mVoTemps.get(i).getTime() +" :: ");
        mBuilder.append(mVoTemps.get(i).getAdd() +" :: ");
    }

    Log.d("Time : ", mBuilder1.toString());
    Log.d("Address : ", mBuilder.toString());

Upvotes: 1

Anonymous
Anonymous

Reputation: 86286

Like others I recommend not reinventing the wheel, and I also recommend discarding the old and outdated classes SimpleDateFormat and Date. We have so much better these days.

Given

static final DateTimeFormatter dtf = DateTimeFormatter.ofPattern("h:mm a", Locale.ENGLISH);

we can do

    Collections.sort(listOfTimeStrings, 
                     Comparator.comparing(
                             (String s) -> LocalTime.parse(s.toUpperCase(), dtf)));

This will work nicely for a few hundred strings, maybe more. It will, however, parse each string each time two strings are to be compared. That could be many times. If you want to parse each string only once, instead do:

    List<String> sortedList = listOfTimeStrings.stream()
            .map(String::toUpperCase)
            .map(s -> LocalTime.parse(s, dtf))
            .sorted()
            .map(dtf::format)
            .map(String::toLowerCase)
            .collect(Collectors.toList());

I have taken it literally when you give am and pm in lowercase, so I am converting to uppercase before the parsing and back to lowercase after formatting. Depending on your data you may skip these steps.

Upvotes: 0

ΦXocę 웃 Пepe&#250;pa ツ
ΦXocę 웃 Пepe&#250;pa ツ

Reputation: 48278

Don't reinvent the wheel, use collection (or Lambdas if java8 is allowed) How??: keep the list as strings, but use an Anonymous comparator, in there, parse the string to dates, compare them and there you have it. here a snippet:

List<String> l = new ArrayList<String>();
l.add("8:00 am");
l.add("8:32 am");
l.add("8:10 am");
l.add("1:00 pm");
l.add("3:00 pm");
l.add("2:00 pm");
Collections.sort(l, new Comparator<String>() {

    @Override
    public int compare(String o1, String o2) {
        try {
            return new SimpleDateFormat("hh:mm a").parse(o1).compareTo(new SimpleDateFormat("hh:mm a").parse(o2));
        } catch (ParseException e) {
            return 0;
        }
        }
    });
    System.out.println(l);

Upvotes: 11

Atri
Atri

Reputation: 5831

Here is a short program for what you want to do.

public static void main(String[] args) throws ParseException {
    ArrayList<String> times = new ArrayList<String>();
    times.add("8:00 pm");
    times.add("8:00 am");
    times.add("7:00 pm");
    times.add("7:00 am");
    ArrayList<Date> dates = new ArrayList<Date>();
    DateFormat format = new SimpleDateFormat("h:m a", Locale.ENGLISH);
    for(String time : times){
        dates.add(format.parse(time));
    }
    Collections.sort(dates);
    System.out.println(dates);
}

Steps:

  • Convert each string to a standardized Date
  • Sort using Collections.sort()

Upvotes: 1

Henning Luther
Henning Luther

Reputation: 2075

Convert your Strings to Dates and sort the dates. In Java in general you should always handle the objects as they are, not Strings. Strings are names or other texts, when there is a special meaning of a String you better convert into that meaningful object.

Upvotes: 2

Rohit5k2
Rohit5k2

Reputation: 18112

Use 24 hour time format in your list and then sort it.

You can revert it back to AM and PM anytime.

Upvotes: 0

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