Arrays - Absolute Java - page 347

Creating and Accessing Arrays
In Java, an array is a special kind of object, but it is often more useful to think of it as
a collection of variables all of the same type. For example, an array that behaves like a
collection of five variables of type double can be created as follows:

double [] score = new double [5];
This is like declaring the following to be five variables of type double :

indexed
variable

score[0], score[1], score[2], score[3], score[4]
The individual variables that make up the array are referred to in a variety of different
ways. We will call them indexed variables , though they are also sometimes called
subscripted variables or elements of the array. The number in square brackets is
called an index or a subscript . In Java, indices are numbered starting with 0 , not any
number . The number of indexed variables in an array is called the length or size of the
array. When an array is created, the length of the array is given in square brackets after
the array name. The indexed variables are then numbered (also using square brackets)
starting with 0 and ending with the integer that is one less than the length of the array .
The following example:

subscripted
variable

element

index,
subscript

length, size

double [] score = new double [5];
is really shorthand for the following two statements:

double [] score;
score = new double [5];
The first statement declares the variable score to be of the array type double[] . The
second statement creates an array with five indexed variables of type double and makes
the variable score a name for the array. You may use any expression that evaluates to
a nonnegative int value in place of the 5 in square brackets. In particular, you can fill
a variable with a value read from the keyboard and use the variable in place of the 5 . In
this way, the size of the array can be determined when the program is run.
An array can have indexed variables of any type, as long as they are all of the same
type. This type is called the base type of the array. In our example, the base type of
the array score is double . To declare an array with base type int , simply use the type
name int instead of double when the array is declared and created. The base type of
an array can be any type. In particular, it can be a class type.
Each of the five indexed variables of our example array score can be used just like
any other variable of type double . For example, all of the following are allowed in Java:

base type

score[3] = 32;
score[0] = score[3] + 10;
System.out.println(score[0]);
The five indexed variables of our sample array score are more than just five plain
old variables of type double . That number in square brackets is part of the indexed
variable's name. So, your program can compute the name of one of these variables.