How i can iterate list to get 10 elements each time in java

Question

I have a list with 70 elements.

For Example:

List<Long> dbList = new ArrayList<Long>();

dbList has 70 records. If I send all the records to a query in MySql it takes a long time. So now I want to send each time 10 elements to database query. So I need to iterate over the list in intervals of 10. How can I do this? Is this a good approach to avoid long time when using IN.

SQL Query

select model.boothId, model.panchayat.panchayatId
from Table1 model
where model.panchayat.panchayatId in(:locationValues)
  and model.publicationDate.publicationDateId in (:publicationDateIdsList)
  and model.constituency.id = :id group by model.panchayat.panchayatId

Thanks in advance...

Answer 1

ArrayList#subList is a very efficient operation. You can iterate over ranges of size 10:

for (int i = 0; i < dbList.size(); i += 10) {
   List<Long> sub = dbList.subList(i, Math.min(dbList.size(),i+10)));
   ... query ...
}

Answer 2

If you use Eclipse Collections (formerly GS Collections) and change dbList to a MutableList or something similar, you can write:

MutableList<Long> dbList = ...;
RichIterable<RichIterable<Long>> chunks = dbList.chunk(10);

If you can't change the return type of dbList, you can wrap it in a ListAdapter.

RichIterable<RichIterable<Long>> chunks = ListAdapter.adapt(dbList).chunk(10);

Note: I am a committer for Eclipse Collections.

Answer 3

You can use the subList method in the List interface to divide your list.