10

C H A P T E R

Arrays

Even Solomon in all his glory was not arrayed like one of these.

 Matthew 6:29

J

AVA

arrays

 are objects ( 4.3.1), are dynamically created, and may be assigned

to variables of type

Object

 ( 4.3.2). All methods of class

Object

 may be invoked

on an array.

An array object contains a number of variables. The number of variables may

be zero, in which case the array is said to be

empty

. The variables contained in an

array have no names; instead they are referenced by array access expressions that

use nonnegative integer index values. These variables are called the

components

of the array. If an array has

n

 components, we say

n

 is the

length

 of the array; the

components of the array are referenced using integer indices from 0 to

n

  1 ,

inclusive.

All the components of an array have the same type, called the

component type

of the array. If the component type of an array is

T

, then the type of the array itself

is written

T[]

.

The component type of an array may itself be an array type. The components

of such an array may contain references to subarrays. If, starting from any array

type, one considers its component type, and then (if that is also an array type) the

component type of that type, and so on, eventually one must reach a component

type that is not an array type; this is called the

element type

 of the original array,

and the components at this level of the data structure are called the

elements

 of the

original array.

There is one situation in which an element of an array can be an array: if the

element type is

Object

, then some or all of the elements may be arrays, because

any array object can be assigned to any variable of type

Object

.

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