public <T> T[] toArray(T[] a, int offset) {
if (size() + offset < a.length) a = Arrays.copyOf(a, size() + offset);
BTree.toArray(tree, lowerBound, upperBound + 1, a, offset);
return a;
}
public <T> T[] toArray(T[] a, int offset) {
int size = size();
if (a.length < size + offset) a = Arrays.copyOf(a, size);
BTree.toArray(tree, a, offset);
return a;
}