EXPRESSIONS

Runtime Evaluation of Array Access

15.12.1

15.12   Array Access Expressions

An array access expression refers to a variable that is a component of an array.

ArrayAccess:

ExpressionName

 [

Expression

 ]

PrimaryNoNewArray

 [

Expression

 ]

An array access expression contains two subexpressions, the

array reference

expression

 (before the left bracket) and the

index expression

 (within the brackets).

Note that the array reference expression may be a name or any primary expression

that is not an array creation expression ( 15.9).

The type of the array reference expression must be an array type (call it

T

[]

,

an array whose components are of type

T

) or a compile time error results. Then

the type of the array access expression is

T

.

The index expression undergoes unary numeric promotion ( 5.6.1); the pro 

moted type must be

int

.

The result of an array reference is a variable of type

T

, namely the variable

within the array selected by the value of the index expression. This resulting vari 

able, which is a component of the array, is never considered

final

, even if the

array reference was obtained from a

final

 variable.

15.12.1   Runtime Evaluation of Array Access

An array access expression is evaluated using the following procedure:

First, the array reference expression is evaluated. If this evaluation completes

abruptly, then the array access completes abruptly for the same reason and the

index expression is not evaluated.

Otherwise, the index expression is evaluated. If this evaluation completes

abruptly, then the array access completes abruptly for the same reason.

Otherwise, if the value of the array reference expression is

null

, then a

NullPointerException

is thrown.

Otherwise, the value of the array reference expression indeed refers to an

array. If the value of the index expression is less than zero, or greater than or

equal to the array's length, then an

IndexOutOfBoundsException

 is thrown.

Otherwise, the result of the array reference is the variable of type

T

, within the

array, selected by the value of the index expression. (Note that this resulting

variable, which is a component of the array, is never considered

final

, even

if the array reference expression is a

final

 variable.)

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