Blender – obtain a smooth cylinder

Solution 1: create a new one

1. Create a new cylinder – from the menu Add -> Mesh -> Cylinder
2. otherwise SHIFT+A as shortcut -> Mesh -> Cylinder
3. adjust the number of vertices until you are satisfied

Solution 2: work with modifiers

1. select the cylinder you need to smooth
2. go to modifiers
3. add as first “Edge Split”
4. add the second most known “Subdivision”
5. adjust the “levels viewport” up to 3

For the second solution, thank you to TheAdamBomb.