Java get last element of a collection

Question

I have a collection, I want to get the last element of the collection. What\'s the most straighforward and fast way to do so?

One solution is to first toArray(), and

Answer 1

Well one solution could be:

list.get(list.size()-1)

Edit: You have to convert the collection to a list before maybe like this: new ArrayList(coll)

Answer 2

If you have Iterable convert to stream and find last element

 Iterator<String> sourceIterator = Arrays.asList("one", "two", "three").iterator();

 Iterable<String> iterable = () -> sourceIterator;


 String last = StreamSupport.stream(iterable.spliterator(), false).reduce((first, second) -> second).orElse(null);

Answer 3

A Collection is not a necessarily ordered set of elements so there may not be a concept of the "last" element. If you want something that's ordered, you can use a SortedSet which has a last() method. Or you can use a List and call mylist.get(mylist.size()-1);

If you really need the last element you should use a List or a SortedSet. But if all you have is a Collection and you really, really, really need the last element, you could use toArray() or you could use an Iterator and iterate to the end of the list.

For example:

public Object getLastElement(final Collection c) {
    final Iterator itr = c.iterator();
    Object lastElement = itr.next();
    while(itr.hasNext()) {
        lastElement = itr.next();
    }
    return lastElement;
}

Answer 4

Or you can use a for-each loop:

Collection<X> items = ...;
X last = null;
for (X x : items) last = x;

Answer 5

A reasonable solution would be to use an iterator if you don't know anything about the underlying Collection, but do know that there is a "last" element. This isn't always the case, not all Collections are ordered.

Object lastElement = null;

for (Iterator collectionItr = c.iterator(); collectionItr.hasNext(); ) {
  lastElement = collectionItr.next();
}

Answer 6

This should work without converting to List/Array:

collectionName.stream().reduce((prev, next) -> next).orElse(null)