Two different ArrayList merge? [closed]

Answer 1

If there are any realtionships between SublistLocalData class and the Localdata class you can create a class that is a super class both of them or an Interface which the two classes implements. Say you have this class : class AbstractSuperClass {} Then : Here how to declare a list of the superClass : List<AbstractSuperClass> list; Using this list, you can add any type of AbstractSuperClass (classes that inherits from it like SublistLocalData and Localdata ) You can then write :

list.add(new SublistLocalData());

orlist.add(new Localdata());

Answer 2

Question What should i do to solve this ?

Answer: Find a tutorial about Collection framework in Java and read it.

If you want to store objects of different type in single list, you should create a list that can accept any object. Every object in Java inherit from Object class. Therefore you need to create something like:

private List<Object> list4Everything = new ArrayList<>();

EDIT:

How ever if you have same object and you just want to merge two already existing list into new single one. You should use the method List#addAll(Collection c)

Lest do it on example, we will have three lists:

private List<YourType> list1 = new ArrayList<>();
private List<YourType> list2 = new ArrayList<>();
private List<YourType> mergeResult = new ArrayList<>();

You have various option to insert all data from list1 and 'list2' into mergeResult

Option 1 - Using addAll of megeResult.

mergeResult.addAll(list1);
mergeResult.addAll(list2);

Option 2 - Do it by hand.

for(YourType yt : list1) { //Itereate throug every item from list1
   mergerResult.add(yt); //Add found item to mergerResult
}

for(YourType yt : list1) { //Itereate throug every item from list2
   mergerResult.add(yt); //Add found item to mergerResult
}

Note: In this solution you have possibility to select witch item is added to meregeResult.

So for example if we would like to have distinct result we could do something like this.

for(YourType yt : list1) { //Itereate throug every item from list1
  if(mergerResult.contains(yt) == false) { //We check that item, already exits in mergeResult
     mergerResult.add(yt); //Add found item to mergerResult
  }
}

for(YourType yt : list1) { //Itereate throug every item from list2
  if(mergerResult.contains(yt) == false) { //We check that item, already exits in mergeResult
   mergerResult.add(yt); //Add found item to mergerResult
   }
}

---

As we perform twice the same operation we could create a utilities class.

public static <T> boolean addAllNotContained(Collection<? super T> traget, Collection<? super T> source) {

   //We should assure first that target or source are not null

   int targetSize = target.size();

   for(T item: source) {
     if(target.contains(item) == false) {
        target.add(item);
     }
   }

   return targetSize != target.size();
}

Note: To have similar result of distinct merge you could use jest Set. It is created to not store duplicates.

The another option is too use already created framework that extend default Java one. The options are guava with iterables and apache commons