Java Reference
In-Depth Information
1
// Fig. 7.2: InitArray.java
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// Initializing the elements of an array to default values of zero.
3
4
public class
InitArray
5
{
6
public static void
main(String[] args)
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{
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// declare variable array and initialize it with an array object
int
[] array =
new
int[
10
];
// create the array object
9
10
11
System.out.printf(
"%s%8s%n"
,
"Index"
,
"Value"
);
// column headings
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13
// output each array element's value
for
(
int
counter =
0
; counter < array.length; counter++)
System.out.printf(
"%5d%8d%n"
, counter, array[counter]);
14
15
16
}
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}
// end class InitArray
Index Value
0 0
1 0
2 0
3 0
4 0
5 0
6 0
7 0
8 0
9 0
Fig. 7.2
|
Initializing the elements of an array to default values of zero.
The
for
statement (lines 14-15) outputs the index (represented by
counter
) and value
of each array element (represented by
array[counter
]). Control variable
counter
is initially
0
—index values start at 0, so using
zero-based counting
allows the loop to access every ele-
ment of the array. The
for
's loop-continuation condition uses the expression
array.length
(line 14) to determine the length of the array. In this example, the length of the array is 10,
so the loop continues executing as long as the value of control variable
counter
is less than
10. The highest index value of a 10-element array is 9, so using the less-than operator in the
loop-continuation condition guarantees that the loop does not attempt to access an element
beyond
the end of the array (i.e., during the final iteration of the loop,
counter
is
9
). We'll
soon see what Java does when it encounters such an
out-of-range index
at execution time.
You can create an array and initialize its elements with an
array initializer
—a comma-sep-
arated list of expressions (called an
initializer list
) enclosed in braces. In this case, the array
length is determined by the number of elements in the initializer list. For example,
int
[] n = {
10
,
20
,
30
,
40
,
50
};
creates a
five
-element array with index values
0
-
4
. Element
n[0]
is initialized to
10
,
n[1]
is initialized to
20
, and so on. When the compiler encounters an array declaration that in-
