The BlockHarvestDrops Event is fired whenever a block is about to drop its items.
You can modify the block list as well as the overall drop chance. Set latter to 1 if you do all chance handling beforehand.
You will need to cast the event in the function header as this class:
You can, of course, also import the class before and use that name then.
Event interface extensions
BlockHarvestDrops Events implement the following interfaces and are able to call all of their methods/getters/setters as well:
The following information can be retrieved from the event:
Adding an item to the list
You can either addAssign the list or use the method to add an item to the list:
event.drops += <minecraft:coal>; event.addItem(<minecraft:coal>);