Java Reference
In-Depth Information
Compare this to our original, very simple
HelloWorld.java
file. Notice right at the
top, the
package
statement and later the
public class
statement now each refer
to
SkyCmd
instead of
HelloWorld
.
Let's take a closer look at how a plugin handles a chat command like
/sky
.
Handle Chat Commands
The bit with the
@Command
at
❶
tells the system that this function,
skyCommand
,
is responsible for handling the
/sky
command. That is, when the player types
the
/sky
command, your
skyCommand
function will be called.
The first thing we need to check is a little awkward; it turns out that the
MessageReceiver
that gets passed to us here may not be a
Player
. It could be a
Player
object, or who knows what else. We want to make sure it's really a
Player
,
so we'll check for that explicitly at
❷
, using the Java keyword
instanceof
. This
tests to see if the thing passed in is really a
Player
. If it is, then we're going to
do the bulk of the command starting at
❸
. (If it's not a
Player
, then it's probably
a console command, if you want to allow those.)
The
skyCommand
function begins with another bit of magic, just like we saw
with parent/child recipes at the end of
Chapter 5,
Plugins Have Objects
, on
page 67
. Now that we've confirmed the variable
caller
is really of type
Player
(not
just a
MessageReceiver
or any other parent or child), we can convert it to the
type
Player
, using a
cast
operator.
So the expression
(Player)caller
returns the variable
caller
, converted with a cast
operator to the type
Player
so you can assign it to the variable
me
. It sounds
messy, and it is a bit, but it's also something you can just copy and paste,
as we'll be using this little recipe in almost every command plugin to get a
Player
object.
Now that we have a real
Player
object referenced by
me
, we can get the list of
all living entities with
me.getWorld().getEntityLivingList()
, which will get us all the
living entities in this world and return them in a
List
that we'll go through with
a
for
loop.
We'll go over the details of lists in the next chapter, but first we'll look at how
Location
objects work. In this case, we're setting the variable
target
to each entry
in the list of entities as we go through the
for
loop. If the
target
is not a fellow
player, then we want to fling it skyward, which we do by changing its location
with a
teleportTo()
.
