Java Reference
In-Depth Information
Declaring and Creating an Array
Declare an array name and create an array in almost the same way that you create and
name objects of classes. There is only a slight difference in the syntax.
SYNTAX
Base_Type
[]
Array_Name
=
new
Base_Type
[
Length
];
The
Length
may be given as any expression that evaluates to a nonnegative integer. In
particular,
Length
can be an
int
variable.
EXAMPLES
char
[] line =
new char
[80];
double
[] reading =
new double
[300];
Person[] specimen =
new
Person[100];
Person
is a class.
Instead of writing an integer constant in the square brackets, you can use any
expression that evaluates to an integer that is at least
0
and at most
4
. So, the following
is allowed:
System.out.println(score[index] + " is at position " + index);
where
index
is a variable of type
int
that has been given one of the values
0
,
1
,
2
,
3
,
or
4
.
When we refer to these indexed variables grouped together into one collective item,
we will call them an
array
. So, we can refer to the array named
score
(without using
any square brackets).
The program in Display 6.1 shows an example of using our sample array
score
as
five indexed variables, all of type
double
.
Note that the program can compute the name of an indexed variable by using a
variable as the index, as in the following
for
loop:
for
(index = 0; index < 5; index++)
System.out.println(score[index] + " differs from max by "
+ (max - score[index]));
Do not confuse the three ways to use the
square brackets
[]
with an array name.
First, the square brackets can be used to create a type name, such as the
double[]
in
the following:
square
brackets [ ]
double
[] score;
Second, the square brackets can be used with an integer value as part of the special
syntax Java uses to create a new array, as in
score =
new double
[5];