Java Reference
In-Depth Information
state = false;
sets the value of the variable
state
to
false
.
At this point you can't do much with a
boolean
variable, other than to set its value to
true
or
false
,
but as you see in the next chapter,
boolean
variables become much more useful in the context of decision
making in a program, particularly when you can use expressions that produce a result of type
boolean
.
Several operators combine
boolean
values, including operators for
boolean
AND,
boolean
OR, and
boolean
negation (these are
&&
,
||
, and
!
, respectively), as well as comparison operators that produce a
boolean
result. Rather than go into these here in the abstract, I defer discussion until the next chapter where
I also go into how you can apply them in practice to alter the sequence of execution in a program.
NOTE
Note that variables of type
boolean
differ from the other primitive data types in that
theycannotbecasttoanyotherbasictype,andtheotherprimitivetypescannotbecasttotype
boolean
.
OPERATOR PRECEDENCE
I have already introduced the idea of a pecking order for operators that determines the sequence in which
they are executed in a statement. A simple arithmetic expression such as 3 + 4 * 5 results in the value 23
because the multiply operation is executed first — it takes precedence over the addition operation. I can now
formalize the position by classifying all the operators present in Java according to their precedence. Each
operator in Java has a set priority or precedence in relation to the others, as shown in the following table.
Operators with a higher precedence are executed before those of a lower precedence. Precedence is highest
for operators in the top line in the table, down through to the operators in the bottom line, which have the
lowest precedence. Operators that appear on the same line of the table have the same precedence (see
Table
TABLE 2-10
:
The Associativity of Operator Precedence Groups
OPERATOR PRECEDENCE GROUP
ASSOCIATIVITY
(), [], postfix ++, postfix −−
left
unary +, unary −, prefix ++, prefix −−, ~, !
right
(type), new
left
*, /, %
left
+, −
left
<<, >>, >>>
left
< ,<= , >, >=, instanceof
left
==, !=
left
&
left
^
left
|
left
&&
left
||
left
