Can duplicate a number of items in Survival (cheat)

In Minecraft there is a bug/cheat in survival. Basically you put a chest on a sticky piston with a large chest next to the piston. You then put the desired item that you want to duplicate in the chest above the sticky piston. Then you get the sticky piston to go up and down. There's probably something else that you have to do but I'm not completely sure how as another friend did this. Please help as this bug is ruining my friends survival world.

Sorry about the insufficient detail on Operating System Version and Affects Version/s as this "cheat" was not done on my device.

Thanks for your help!