How to Sort Date in descending order From Arraylist Date in android

Question

I have an ArrayList which stores Dates and I sorted them in descending order  Now I want to display them in a ListView  This is what I did so far    spndata setOnItemSelectedListener new OnItemSelectedListener                 public void onItemSelected AdapterView lt   gt  arg0  View arg1                      int position  long arg3                     switch  position                    case 0                      list   DBAdpter requestUserData assosiatetoken                       for  int i   0  i  lt  list size    i                              if  list get i  lastModifiedDate    null                                lv setAdapter new MyListAdapter                                      getApplicationContext    list                                                                        break                  case 1                      list   DBAdpter requestUserData assosiatetoken                        Calendar c   Calendar getInstance                        SimpleDateFormat df3   new SimpleDateFormat  MM dd yyyy hh mm ss a                            String formattedDate3   df3 format c getTime                                                 Log v  log tag    Date      formattedDate3                        for  int i   0  i  lt  list size    i                                                       if  list get i  submitDate    null                                                               String sDate   list get i  submitDate                                                            SimpleDateFormat df4   new SimpleDateFormat  MM dd yyyy hh mm ss a                                    String formattedDate4   df4 format sDate                                Map lt Date  Integer gt  dateMap   new TreeMap lt Date  Integer gt  new Comparator lt Date gt                                        public int compare Date formattedDate3  Date formattedDate4                                         return formattedDate3 compareTo formattedDate4                                                                                                  lv setAdapter new MyListAdapter                                      getApplicationContext    list                                                                        break                  case 2                       break                   case 3                       break                   default                      break                                                public void onNothingSelected AdapterView lt   gt  arg0

User · Accepted Answer

Create Arraylist lt Date gt  of Date class  And use Collections sort   for ascending order       See sort List lt T gt  list      Sorts the specified list into ascending order  according to the natural ordering of its elements    For Sort it in descending order See Collections reverseOrder    Collections sort yourList  Collections reverseOrder

User · Answer

Date s compareTo   you re using will work for ascending order   To do descending  just reverse the value of compareTo   coming out  You can use a single Comparator class that takes in a flag enum in the constructor that identifies the sort order  public int compare MyObject lhs  MyObject rhs         if SortDirection Ascending    m sortDirection            return lhs MyDateTime compareTo rhs MyDateTime              return rhs MyDateTime compareTo lhs MyDateTime       You need to call Collections sort   to actually sort the list   As a side note  I m not sure why you re defining your map inside your for loop  I m not exactly sure what your code is trying to do  but I assume you want to populate the indexed values from your for loop in to the map

User · Answer

If date in string format convert it to date format for each object    String argmodifiledDate    2014-04-06 22 26 15   SimpleDateFormat  format   new SimpleDateFormat  yyyy-MM-dd HH mm ss                  try                               this modifiledDate   format parse argmodifiledDate                             catch  ParseException e                                 e printStackTrace                    Then sort the arraylist in descending order    ArrayList lt Document gt  lstDocument  this objDocument getArlstDocuments            Collections sort lstDocument  new Comparator lt Document gt                    public int compare Document o1  Document o2                      if  o1 getModifiledDate      null    o2 getModifiledDate      null                      return 0                         return o2 getModifiledDate   compareTo o1 getModifiledDate

User · Answer

Easier alternative to above answers   If Object Model Class POJO  contains the date in String datatype   private void sortArray ArrayList lt myObject gt  arraylist    SimpleDateFormat simpleDateFormat   new SimpleDateFormat  yyyy-MM-dd T HH mm ss SSS Z       your own date format if  reports    null        Collections sort arraylist  new Comparator lt myObject gt               Override         public int compare myObject o1  myObject o2                try                   return simpleDateFormat parse o2 getCreated at    compareTo simpleDateFormat parse o1 getCreated at                    catch  ParseException e                    e printStackTrace                    return 0                                     If Object Model Class POJO  contains date in Date datatype  private void sortArray ArrayList lt myObject gt  arrayList    if  arrayList    null        Collections sort arrayList  new Comparator lt myObject gt               Override         public int compare myObject o1  myObject o2                return o2 getCreated at   compareTo o1 getCreated at                      The above code is for sorting the array in descending order of date  swap o1 and o2 for ascending order

User · Answer

Just add like this in case 1  like this   case 0       list   DBAdpter requestUserData assosiatetoken        Collections sort list  byDate        for  int i   0  i  lt  list size    i               if  list get i  lastModifiedDate    null                 lv setAdapter new MyListAdapter                       getApplicationContext    list                           break    and put this method at end of the your class  static final Comparator lt All Request data dto gt  byDate   new Comparator lt All Request data dto gt          SimpleDateFormat sdf   new SimpleDateFormat  MM dd yyyy hh mm ss a         public int compare All Request data dto ord1  All Request data dto ord2            Date d1   null          Date d2   null          try               d1   sdf parse ord1 lastModifiedDate               d2   sdf parse ord2 lastModifiedDate             catch  ParseException e                   TODO Auto-generated catch block             e printStackTrace                        return  d1 getTime    gt  d2 getTime     -1   1         descending         return  d1 getTime    gt  d2 getTime     1   -1         ascending

User · Answer

Date is Comparable so just create list of List lt Date gt  and sort it using Collections sort    And use Collections reverseOrder   to get comparator in reverse ordering   From Java Doc     Returns a comparator that imposes the reverse ordering of the specified comparator  If the specified comparator is null  this method is equivalent to reverseOrder    in other words  it returns a comparator that imposes the reverse of the natural ordering on a collection of objects that implement the Comparable interface

[java] How to Sort Date in descending order From Arraylist Date in android?

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