Java Reference
In-Depth Information
cakeHeight = 50;
❷
int
cakeHeight;
cakeHeight = 5;
me.chat(
"2) cake height is "
+ cakeHeight);
// Print it
makeCakes(me);
}
}
public void
makeCakes(Player me) {
me.chat(
"3) cake height is "
+ cakeHeight);
// Print it
Location loc = me.getLocation();
loc.setY(loc.getY() + 2);
setBlockAt(loc, BlockType.Stone);
for
(
int
i = 0;i < cakeHeight;i++) {
loc.setY(loc.getY() + 1);
setBlockAt(loc, BlockType.Cake);
}
}
}
When run, this code will print out the value of
cakeHeight
three times. Notice
that there are two declarations of the variable
cakeHeight
, one at
❶
and
another at
❷
.
What will this code print out, and how many cakes will end up in the tower?
Try to figure it out first. Then compile and install using
build.sh
as usual.
What Happened?
Welcome to the wonderfully confusing world of
shadowing
.
In this piece of code, a variable named
cakeHeight
is declared at the top of the
plugin. This is the variable you would expect to access anywhere within the
plugin—starting on that line and ending at the matching closing brace,
}
.
But then on the line at
❷
we declare another variable with the very same
name. From this point until the next closing brace, }, any time we mention
cakeHeight
we'll be working with this local one, not the class-level one. This
local version
shadows
the class version. So when we set it to 5 and then print
it, we're modifying this local version.
Calling
makeCakes
then uses the class version to build the tower. The
makeCakes
function has no knowledge of the shadowed variable inside the
cakeTowerCommand
function. So you end up with fifty blocks; not a hundred, and not five.
