15.5

Normal and Abrupt Completion of Evaluation

EXPRESSIONS

15.5   Normal and Abrupt Completion of Evaluation

No more: the end is sudden and abrupt.

 William Wordsworth,

Apology for the Foregoing Poems

 (1831)

Every expression has a normal mode of evaluation in which certain computational

steps are carried out. The following sections describe the normal mode of evalua 

tion for each kind of expression. If all the steps are carried out without an excep 

tion being thrown, the expression is said to

complete normally

.

If, however, evaluation of an expression throws an exception, then the expres 

sion is said to

complete abruptly

. An abrupt completion always has an associated

reason

, which is always a

throw

 with a given value.

Run time exceptions are thrown by the predefined operators as follows:

A class instance creation expression ( 15.8), array creation expression

( 15.9), or string concatenation operatior expression ( 15.17.1) throws an

OutOfMemoryError

 if there is insufficient memory available.

An array creation expression throws an

ArrayNegativeSizeException

 if

the value of any dimension expression is less than zero ( 15.9).

A field access ( 15.10) throws a

NullPointerException

 if the value of the

object reference expression is

null

.

A method invocation expression ( 15.11) that invokes an instance method

throws a

NullPointerException

 if the target reference is

null

.

An array access ( 15.12) throws a

NullPointerException

 if the value of

the array reference expression is

null

.

An array access ( 15.12) throws an

IndexOutOfBoundsException

 if the

value of the array index expression is negative or greater than or equal to the

length

 of the array.

A cast ( 15.15) throws a

ClassCastException

 if a cast is found to be imper 

missible at run time.

An integer division ( 15.16.2) or integer remainder ( 15.16.3) operator

throws an

ArithmeticException

 if the value of the right hand operand

expression is zero.

An assignment to an array component of reference type ( 15.25.1) throws an

ArrayStoreException

 when the value to be assigned is not compatible with

the component type of the array.

304