Java Reference
In-Depth Information
cedencelevelis10andmultiplication'sprecedencelevelis11,whichmeansthatmul-
tiplication is performed before addition.
Precedencecanbecircumventedbyintroducingopenandcloseparentheses,
(
and
)
,
intotheexpression,wheretheinnermostpairofnestedparenthesesisevaluatedfirst.For
example,2*
((60+3)*6)
resultsin
(60+3)
beingevaluatedfirst,
(60+3)*6
being
evaluatednext,andtheoverallexpressionbeingevaluatedlast.Similarly,intheexpres-
sion
60/(3-6)
, subtraction is performed before division.
Duringevaluation,operatorswiththesameprecedencelevel(e.g.,additionandsub-
traction,whichbothhavelevel10)areprocessedaccordingtotheir
associativity
(aprop-
ertythatdetermineshowoperatorshavingthesameprecedencearegroupedwhenpar-
entheses are missing).
Forexample,expression
9*4/3
isevaluatedasifitwas
(9*4)/3
because
*
and
/
areleft-to-rightassociativeoperators.Incontrast,expression
x=y=z=100
isevaluated
asifitwas
x=(y=(z=100))
—
100
isassignedto
z
,
z
'snewvalue(100)isassigned
to
y
,and
y
'snewvalue(100)isassignedto
x
-because
=
isaright-to-leftassociative
operator.
MostofJava'soperatorsareleft-to-rightassociative.Right-to-leftassociativeoperat-
ors include assignment, bitwise complement, cast, compound assignment, conditional,
logicalcomplement,objectcreation,predecrement,preincrement,unaryminus,andun-
ary plus.
Note
Unlike languages such as C++, Java doesn't let you overload operators.
However, Java overloads the
+
,
++
, and
--
operator symbols.
Statements
Statementsaretheworkhorsesofaprogram.Theyassignvaluestovariables,controla
program'sflowbymakingdecisionsand/orrepeatedlyexecutingotherstatements,and
perform other tasks. A
statement
can be expressed as a simple statement or as a com-
pound statement:
• A
simple statement
isasinglestandalonesourcecodeinstructionforperforming
some task; it's terminated with a semicolon.
• A
compound statement
isa(possiblyempty)sequenceofsimpleandothercom-
poundstatementssandwichedbetweenopenandclosebracedelimiters—a
de-
limiter
isacharacterthatmarksthebeginningorendofsomesection.Amethod
body(e.g.,the
main()
method'sbody)isanexample.Compoundstatements
