Big O

Question

I still have so much confusion when it comes to Big O notation. I know its very simple but still struggle with picking them out. But, my question is. What's the Big O notation for this formula? I feel that its O(n) but I'm unsure.

public void enqueue(T element) {
if(size() == queue.length)
expandCapacity();

queue[rear] = element;
rear = (rear+1) % queue.length;

numElements++;
}

Answer 1

Pretty much everything in that method is O(1) besides probably expandCapacity().
Therefore the whole method will obtain the O( ) of whatever the O( ) of expandCapacity() is. That *should* be O(n) but depends on implementation after all.