Java Reference
In-Depth Information
Act Like a Stack
Even though this is a
DataAccess
object, we are free to add other functions and
bits of data to it to help make building our plugin easier. So from the perspec-
tive of the main plugin, we'd like to be able to treat a
SavedLocation
for a given
player as a stack of
Location
s. That means we'll need to expose at least a public
push
and
pop
function.
Here's the first hitch:
location_strings
is declared as an
ArrayList<String>
, not a
Stack
.
So how would you implement
push
and
pop
using just a plain old list?
Well, the push is easy: an array
add
method will add a new item to the end of
the list. So you just use that for the push.
In order to pop the stack, you have to
remove
the last item in the list using its
index, the
size()
of the list minus one.
Okay, that sounds reasonable. In the public
push
functions, you'll need to
read this player's stack from the database; call an internal, private function
to actually push that location onto the stack; then save it back to the database.
pop
will be similar: read from the database, pop the stack, and write the new
stack back to the database. If you remember back in the
BackCmd
plugin, it
wasn't just enough to pop the latest value—we had to use an
equalsIsh
function
to make sure we'd moved far enough away from the teleport location.
Putting it all together, the public functions in
SavedLocation
would look like this:
public void
push(Location loc) {
myRead(player_name);
//Make sure previous location is different if it exists
if
(peek_stack() == null ||
!equalsIsh(peek_stack(), loc)) {
push_stack(loc);
myWrite();
}
}
public
Location pop(Location here) {
myRead(player_name);
if
(location_strings.size() == 0) {
return
null;
}
Location loc = pop_stack();
myWrite();
return
loc;
}
