The Bukkit API allows a programmer to do more than simply cancel an event. Depending on the event, you are able to modify many aspects of it. In this next project we will modify zombies as they spawn. Every time a zombie spawns we will give it 40 health rather than the default 20. This will make zombies more difficult to kill.
Create a new project as you would for any plugin. We will call this plugin MobEnhancer. Similar to the NoRain plugin, have the main class implement Listener and add the following line of code to the onEnable method to register your EventHandlers:
getServer().getPluginManager().registerEvents(this, this);
For this project, we will have one EventHandler which listens for mobs spawning. This would be the CreatureSpawnEvent. This event has many methods that we can call to either modify the event or gain more information about it. We only wish to modify zombies that are spawned, so the first thing we will add is an if statement checking to see...