An array is a collection of data storage locations, each of which holds the same type of data. Think of an array
as a "box"
drawn in memory with a series of subdivisions, called elements, to store the data.
The box below could represent an array of 10 integers.
While this array contains only 10 elements, arrays are traditionally used to handle large amounts of data.
It is important to remember that all of the elements in an array must contain the same type of data.
Let's consider a programming situation "with" and "without"
the use of an array:
| Without an Array |
Memory |
| Suppose you must calculate the average of 3 integer values: |
score1 =
reply.nextInt( );
score2 = reply.nextInt( );
score3 = reply.nextInt( );
avg = (score1 + score2 + score3) / 3;
Yes, this will be integer division. |
Looking good!
But what if there were 50 scores? You would need 50
separate variable names with 50 lines of input. Yeek! |
| OK! If you have to deal with a
large number of scores, you could use a loop. |
int sum = 0;
for ( i = 1; i <= 50; i++ )
{
System.out.print("Enter score");
score = reply.nextInt( );
sum = sum + score;
}
avg = sum / 50.0; |
Still looking good! But what if,
after finding the average, you need to find how many scores
were above/below the average? Yeek! The only
score entered by the user that is left in memory is the last
one. |
| With an Array |
You can see
that dealing with large amounts of data can present potential
problems, as shown above. With an array, however, only one
variable name is needed and all entries will remain in the
memory for future use. Here we have an array named scores (one name, not 50 separate
names) with 50 cells to hold the entries. All entries will
remain in the memory for future use. (Not all 50
cells are shown in the array below.)
scores
scores is the
name of a 50 element (cell) array. The elements are like mailboxes in a
large
apartment complex. The "name of the array"
is the address of the apartment complex where all of the mailboxes
reside.
 |
Mantra:
The name of the array is the address
of the first element of the array! |
|
|
