Java Reference
In-Depth Information
Array Index Operator
The array index operator (
[]
) accesses an array element by presenting the location
of that element as an integer
index
. This operator is specified after an array variable's
name; for example,
ages[0]
.
Indexes are relative to 0, which implies that
ages[0]
accesses the first element,
whereas
ages[6]
accesses the seventh element. The index must be greater than or
equalto0andlessthanthelengthofthearray;otherwise,theJVMthrows
ArrayIn-
dexOutOfBoundsException
(consult
Chapter 3
to learn about exceptions).
Anarray'slengthisreturnedbyappending“
.length
”tothearrayvariable.Forex-
ample,
ages.length
returnsthelengthof(thenumberofelementsin)thearraythat
ages
references.Similarly,
matrix.length
returnsthenumberofrowelementsin
the
matrix
two-dimensionalarray,whereas
matrix[0].length
returnsthenum-
ber of column elements assigned to the first row element of this array.
Assignment Operators
Theassignmentoperator(
=
)assignsanexpression'sresulttoavariable(asin
int x
= 4;
). The types of the variable and expression must agree; otherwise, the compiler
reports an error.
Javaalsosupportsseveralcompoundassignmentoperatorsthatperformaspecificop-
eration and assign its result to a variable. For example, the
+=
operator evaluates the
numericexpressiononitsrightandaddstheresulttothecontentsofthevariableonits
left. The other compound assignment operators behave in a similar way.
Bitwise Operators
ThebitwiseoperatorsconsistofbitwiseAND(
&
),bitwisecomplement(
~
),bitwiseex-
clusiveOR(
^
),andbitwiseinclusiveOR(
|
).Theseoperatorsaredesignedtoworkon
thebinaryrepresentationsoftheircharacterorintegraloperands.Becausethisconcept
canbehardtounderstandifyouhaven'tpreviouslyworkedwiththeseoperatorsinan-
other language, the following example demonstrates these operators:
~0B00000000000000000000000010110101
results
in
11111111111111111111111101001010
0B00011010&0B10110111
results
in
00000000000000000000000000010010
0B00011010^0B10110111
results
in
00000000000000000000000010101101
