Converting a TreeSet to ArrayList?

Question

I have a TreeSet which contains > 100k objects. I have another method which requires ArrayList as an param.

Is there any way I can accomplish this without iterating

Answer 1

ArrayList has a convenience method addAll that fits the bill nicely:

final Set<Object> set = ...
List<Object> list = new ArrayList<Object>(someBigNum);
list.addAll(set);

Answer 2

How about this:

new ArrayList<T>(set);

For Java 7 and later, this can be simplified, as type arguments <T> can be replaced with diamond type <>:

new ArrayList<>(set);

Answer 3

In case one uses Eclipse Collections, which has super-powers and is developed by Goldman Sachs, there is toList():

MutableSortedSet<Object> set = SortedSets.mutable.empty();
...
return set.toList();

Providing a comparator is also possible:

MutableSortedSet<Object> set = SortedSets.mutable.of(comparator);
...
return set.toList();