Game Development Reference
In-Depth Information
of fun with these soon enough. Let's take a look at logical operators next, so we can
work with
Boolean Sets
and compare things in groups, which is also important for
games.
Java Logical Operators:
The Java
logical operators
are similar to the boolean operations (union, intersection,
etc.) that you learned about in school, and allow you to determine if both boolean vari-
ables hold the same value (
AND
), or if one of the boolean variables is different (
OR
),
from the other. There's also a
NOT
operator that reverses the value of any of the com-
pared boolean operands.
Table 3-4
shows Java's three logical operators, and an ex-
ample of each, along with a description.
a Description of Logical Operation
Operator Example
Description
&&
(A && B) is
false
A logical
AND
operator equates to
true
when
BOTH
operands
are the same value.
||
(A || B) is
true
A logical
OR
operator equates to
true
when
EITHER
operand is
the same value.
!
!(A && B)
is true
A logical
NOT
operator
reverses
the
logical state
of the operator
(or set) it is applied to.
Let's use logical operators to enhance the game logic example in the previous sec-
tion by including the
direction
in which the InvinciBagel is moving on the screen. The
existing
facingDirection String
variable will control the direction the InvinciBagel is
facing (and moving in, if in motion). You can now use the following logical operator to
determine if the InvinciBagel is facing left (W, or
W
est); if the
travelingWest
boolean
variable is
true
;
AND
if the hit (or passed) boolean variable on the left-hand side of the
screen,
hitLeftSideScrn
, is also equal to
true
. The modified code for doing this will
include two more boolean variable declarations and initializations and will look like
this:
boolean
changeDirection =
false
; // Create boolean
variable changeDirection,
initialize
to false
boolean
hitLeftSideScrn =
false
; // Create boolean
variable hitLeftSideScrn,
initialize
to false
