Give a detailed description of the zombie pigman farm.

 It uses the block update system of the lava to trigger the portal on and off making zombie pigeons to occasionally spawn and be washed down into a killing chamber. There could be two main issues that stop the farm from working in java which are observers observing different blocks, and zombie pigman spawning inside the portal and not on one side. The second problem is easy to fix by adding a couple of turtle eggs to lure them out but the Observing might not work and won't keep the portal up. I haven't seen this kind of gold farm in java mode. Please help me with this problem.