fairly new person to Java here, I’d like to ask if there’s a way to add an element between two elements or be able to shift all elements to the right or left of an ArrayList and how I could figure out the middle.
For example if I have [3, 5, 8, 10] and I want to insert the number 6, how would I figure out where it fits in ascending order?
Thanks so much
Depends on your need, do you necessary need an ArrayList?
#1) If you need sorting but is the number unique? The provided example is (3, 5, 8, 10) and to add (6). If there is another '3', should the result return (3,3,5,6,8,10)? If NOT, why not consider a NavigableSet/SortedSet such as TreeSet ?
import java.util.*;
...
NavigableSet<Integer> navSet = new TreeSet<>(Arrays.asList(new Integer[]{3,5,8,10});
navSet.add(6); //you'll get 3,5,6,8,10
navSet.add(6); //still get 3,5,6,8,10 -- no extra 6
#2) Is the number non unique but to be ordered ? There is a collection provided by Apache for BAG(combining Set and List). Apache Commmons Collection Bag
import org.apache.commons.collections4.Bag;
import org.apache.commons.collections4.bag.TreeBag;
...
Bag<Integer> treeBag = new TreeBag<>(Arrays.asList(new Integer[]{3,5,6,8,10});
treeBag.add(6); //you'll get 3,5,6,6,8,10
#3) Else if you really need to code it manually. There is always a Collections util to sort it after you add, e.g.
import java.util.*;
List<Integer> arrayList = Arrays.asList(new Integer[]{3,5,5,8,10});
List sortedList = arrayList.stream().parallel().sorted()collect(Collectors.toList());
//you'll get (3,5,5,6,8,10), as it gets sorted again.
Finally, the sorting above for #2 and #3 is always slower as there is an add then re-sort. If you want something that optimized via search while rebuilding the list, like Stephen P provided in the other answer, it may be a better solution. But as always consider your implementation.
NavigableSet rather than Set. Though not technically necessary, it makes intentions explicit as well as makes available the various methods specific to NavigableSet should they be required in further coding. And I changed var name from treeSet to navSet to match.NavigableSet. You might find it interesting.
add(...)takes care of that.