How to find out what's possible

Going to be learning java soon and was wondering how I can find out what I can do with the bukkit api. If I wanted to find out for myself whether or not I could fill an area with item ID X with a plugin I made what would I do to find out if that's possible, aside from checking/knowing other plugins exist.

 

a) depends on what you want to do
b) read the javadocs - not always terribly up to date, but at least you have a solid idea on how some things do what. Reading source code is the best way for me to learn, but it is different for everyone.

 

I'm content with reading source code to learn, I've done that with PHP a bit for some things. Just curious to to what I would need to do to be able to find out if something is possible. I don't know of any plugins with this feature, but making a mob agro another mob. If I were to make it I would use something like LWC where you type the /mobagro command and click the first mob and then the next mob/player, but I do not how ever know if there is some form of array/database that holds what mob has aggression towards what and aside from someone telling me it's not possible at this time how would I be able to find out for myself whether this is possible or not?



Edit;
Was looking through the java docs for bukkit and found...
http://javadoc.lukegb.com/Bukkit/d5..._1_1event_1_1entity_1_1EntityTargetEvent.html
More specifically....
void setTarget (Entity target)
Set the entity that you want the mob to target instead.

I'm assuming there'd be a getEntity() argument that you'd supply to the setTarget()? Still know very little with regards to java so pardon any simple things I'm missing, I've never liked java so I never learnt the basics