# Get the node with the maximum key
	# O(n) in worst case, average is O(h) with h: tree height
	#
	#     var tree = new BinTreeMap[Int, String]
	#     for i in [4, 2, 1, 5, 3, 6, 7, 8] do tree[i] = "n{i}"
	#     assert tree.max == "n8"
	fun max: E do
		assert not_empty: root != null
		return max_from(root.as(not null)).value
	end