This week's book giveaway is in the Design forum. We're giving away four copies of Building Microservices and have Sam Newman on-line! See this thread for details.

If the method just calls the two operations one after the other, then yes, the result is O(n).

If the method has loops or if statements, the result may be different. For example if it loops n times and calls one or more O(n) operations, the result is O(n^2).