Albert Albert - 1 year ago 149
Java Question

How to reverse a list in Java?

I want to have a reversed list view on a list (in a similar way than

provides a sublist view on a list). Is there some function which provides this functionality?

I don't want to make any sort of copy of the list nor modify the list.

It would be enough if I could get at least a reverse iterator on a list in this case though.

Also, I know how to implement this myself. I'm just asking if Java already provides something like this.

Demo implementation:

static <T> Iterable<T> iterableReverseList(final List<T> l) {
return new Iterable<T>() {
public Iterator<T> iterator() {
return new Iterator<T>() {
ListIterator<T> listIter = l.listIterator(l.size());
public boolean hasNext() { return listIter.hasPrevious(); }
public T next() { return listIter.previous(); }
public void remove() { listIter.remove(); }

I just have found out that some
implementations have
which is what I need. Though there is no general such implementation for
. Which is kind of strange because the implementation I have seen in
is general enough to work with any

Answer Source

Guava provides this: Lists.reverse(List)

List<String> letters = ImmutableList.of("a", "b", "c");
List<String> reverseView = Lists.reverse(letters); 
System.out.println(reverseView); // [c, b, a]

Unlike Collections.reverse, this is purely a view... it doesn't alter the ordering of elements in the original list. Additionally, with an original list that is modifiable, changes to both the original list and the view are reflected in the other.

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