10.1

Array Types

ARRAYS

10.1   Array Types

An array type is written as the name of an element type followed by some number

of empty pairs of square brackets

[]

. The number of bracket pairs indicates the

depth of array nesting. An array's length is not part of its type.

The element type of an array may be any type, whether primitive or reference.

In particular:

Arrays with an interface type as the component type are allowed. The ele 

ments of such an array may have as their value a null reference or instances of

any class type that implements the interface.

Arrays with an

abstract

 class type as the component type are allowed. The

elements of such an array may have as their value a null reference or instances

of any subclass of the

abstract

 class that is not itself

abstract

.

Array types are used in declarations and in cast expressions ( 15.15).

10.2   Array Variables

A variable of array type holds a reference to an object. Declaring a variable of

array type does not create an array object or allocate any space for array compo 

nents. It creates only the variable itself, which can contain a reference to an array.

However, the initializer part of a declarator ( 8.3) may create an array, a reference

to which then becomes the initial value of the variable.

Because an array's length is not part of its type, a single variable of array type

may contain references to arrays of different lengths.

Here are examples of declarations of array variables that do not create arrays:

int[] ai;

//

array of

int

short[][] as;

//

array of array of

short

Object[] ao,

//

array of

Object

otherAo;

//

array of

Object

short s,

//

scalar

short

aas[][];

//

array of array of

short

Here are some examples of declarations of array variables that create array

objects:

Exception ae[] = new Exception[3];

Object aao[][] = new Exception[2][3];

int[] factorial = { 1, 1, 2, 6, 24, 120, 720, 5040 };

char ac[] = {  n ,  o ,  t ,    ,  a ,    ,

  S ,  t ,  r ,  i ,  n ,  g  };

String[] aas = { "array", "of", "String", };

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