How to sort the arraylist from hashmap?

Question

Im using hashmap and arraylist... How to sort the arraylist ? eg) In hashmap values are in order like one,two,three,four,five but i stored these values in arraylist the order changed like three,one,five,two,four

In my code groupList,gnamelist and newList are all arraylist... In print sts PLACES are in correct order but while print on NEWLIST PLACES the order changed How to sort this in order?

My code

    HashMap<String, String> map = new HashMap<String, String>();
      // adding each child node to HashMap key => value
      map.put(TAG_PLACE, gname);
      map.put(TAG_HOTEL,lname);
     // adding HashList to ArrayList
      groupList.add(map);
      gnamelist.add(gname);
      System.out.println("PLACES" + gnamelist);
      List<String> newList = new ArrayList<String>(new LinkedHashSet<String>(gnamelist));
      Collections.sort(newList,Collections.reverseOrder());
      System.out.println("NEWLIST PLACES" + newList);

SplinterReality · Accepted Answer · 2013-04-26 11:12:38Z

1

HashSet will store elements in an unordered fashion, and is likely the culprit of your element reordering.

List<String> newList = new ArrayList<String>(new HashSet<String>(gnamelist));

Also consider using LinkedHashMap/LinkedHashSet, which preserves the ordering of elements added to it.

Alternatively try the following:

gnamelist.add(gname);
System.out.println("PLACES" + gnamelist);
List<String> newList = new ArrayList<String>();
newList.addAll(gnamelist);

edited Apr 26, 2013 at 11:12

answered Apr 26, 2013 at 10:48

SplinterReality

3,4101 gold badge25 silver badges45 bronze badges

Sign up to request clarification or add additional context in comments.

2 Comments

SplinterReality Over a year ago

Why are you using the HashSet at all? You can just use AddAll to add all elements from one list to another. (See my revised answer above)

Make it Simple Over a year ago

ok then how to sort the 'grouplist' array in that i have add map values, two values..

Pragnani Kinnera · Accepted Answer · 2013-04-26 10:34:13Z

1

Try

Collections.sort(newList);

Edit:

If you want to sort in reverse use this

Collections.sort(newList,Collections.reverseOrder());

Important:

if you want to preserve insertion order, you need to use TreeSet instead of HashSet as HashSet doesn't preserve insertion order

edited Apr 26, 2013 at 10:34

answered Apr 26, 2013 at 10:10

Pragnani Kinnera

20.2k6 gold badges54 silver badges76 bronze badges

5 Comments

Make it Simple Over a year ago

no i didn't get it in order, now it changed some other order like four,three,two,five,one

Make it Simple Over a year ago

Now also its not in order, now its in some other order..How to use TreeSet

Pragnani Kinnera Over a year ago

@OneManArmy If it doesn't worked then use LinkedHashSet that should for sure

Make it Simple Over a year ago

List<String> newList = new ArrayList<String>(new LinkedHashSet<String>(gnamelist)); Collections.sort(newList,Collections.reverseOrder()); System.out.println("NEWLIST GRADES" + newList); Now also not in ordered...

Pragnani Kinnera Over a year ago

@OneManArmy don't sor t when you use LinkedHashSet

Collectives™ on Stack Overflow

How to sort the arraylist from hashmap?

2 Answers 2

2 Comments

5 Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

2 Answers 2

2 Comments

5 Comments

Your Answer

Sign up or log in

Post as a guest

Related