Java List of Objects sort by specific object which is not sorting

Question

Am having the following JSONArray which am trying to sort it. So, for that am converting my JSONArray into ArrayList then am sorting them and converting back into JSONArray.

Please find the initial JSONArray (which is not in sorting order).

[  
   {  

      "code":"TE-7000-8003-W",
      "id":"13342",

   },
   {  
      "code":"TE-7000-8003",
      "id":"13163",
   },
   {  
      "code":"TE-7000-8003-WK",
     "id":"11573",
   },
   {  
      "code":"TE-7000-8003S",
      "id":"11565",

   },
   {  
      "code":"TE-7000-8003-K",
      "id":"11557",
   }
]

Please find my below code which am converting my JSONArray into ArrayList and sorting them.

Item item=null;
List<Item> newItemList = new ArrayList<Item>();
for (int i=0;i<resultJSONArray.length();i++) {
    JSONObject jobj = resultJSONArray.getJSONObject(i);
    item = new Item();
    item.setId(jobj.optString("id"));
    item.setCode(jobj.optString("code"));
    newItemList.add(item);
}

 newItemList
  .stream()
  .sorted((object1, object2) -> object1.getCode().compareTo(object2.getCode()));

Iterator<Item> itr = newItemList.iterator();
while(itr.hasNext()) {
    Item item1=itr.next();
    System.out.println("Item----->"+item1.getCode());
}

Following is the output am getting which is not sorted order

Item----->TE-7000-8003-W
Item----->TE-7000-8003
Item----->TE-7000-8003-WK
Item----->TE-7000-8003S
Item----->TE-7000-8003-K

Am expecting the result like below :

Item----->TE-7000-8003
Item----->TE-7000-8003S
Item----->TE-7000-8003-K
Item----->TE-7000-8003-W
Item----->TE-7000-8003-WK

You're not assigning the result of the sorting operation to anything. So you're printing the original, not sorted list. Just use list.sort() if you want to sort in-place. — JB Nizet
– JB Nizet, Commented Sep 19, 2018 at 14:09
Use newItemList.sort(yourComparator) to sort a list instead. — kumesana
– kumesana, Commented Sep 19, 2018 at 14:10

Gabriel Dinant · Accepted Answer · 2019-04-12 12:31:36Z

8

When you create a stream and use sorted you don't change the actual list. So you could do the following:

List<Item> sortedItemList =newItemList
.stream()
.sorted((object1, object2) -> object1.getCode().compareTo(object2.getCode()))
.collect(Collectors.toList());

or better sort the list with the sort method

newItemList
.sort((object1, object2) -> object1.getCode().compareTo(object2.getCode()));

And you could use Comparator.comparing(Item::getCode) to replace the comparator

newItemList
.sort(Comparator.comparing(Item::getCode));

edited Apr 12, 2019 at 12:31

Gabriel Dinant

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answered Sep 19, 2018 at 14:11

Matthieu Gabin

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1 Comment

JB Nizet Over a year ago

And the comparator could be simplified to Comparator.comparing(Item::getCode)

drowny · Accepted Answer · 2018-09-19 14:39:33Z

3

Use a simple Comparator to apply on your list just like that ;

newItemList
.sort((firstObj, secondObj) -> firstObj.getCode().compareTo(secondObj.getCode()));

Or more simple ;

newItemList.sort(Comparator.comparing(Item::getCode)); //dont forget to write getter method of Code variable.

edited Sep 19, 2018 at 14:39

answered Sep 19, 2018 at 14:19

drowny

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2 Comments

JB Nizet Over a year ago

Item::getCode can't possibly be a Comparator. You probably mean Comparator.comparing(Item::getCode)

drowny Over a year ago

Thanks for your attention @JBNizet :)

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