TYPES, VALUES, AND VARIABLES

Reference Types and Values

4.3

Boolean expressions determine the control flow in several kinds of statements:

The

if

 statement ( 14.8)

The

while

 statement ( 14.10)

The

do

 statement ( 14.11)

The

for

 statement ( 14.12)

A

boolean

 expression also determines which subexpression is evaluated in the

conditional

? :

 operator ( 15.24).

Only

boolean

 expressions can be used in control flow statements and as the

first operand of the conditional operator

? :

. An integer

x

 can be converted to a

boolean

, following the C language convention that any nonzero value is

true

, by

the expression

x!=0

. An object reference

obj

 can be converted to a

boolean

,

following the C language convention that any reference other than

null

 is

true

,

by the expression

obj!=null

.

A cast of a

boolean

 value to type

boolean

 is allowed ( 5.1.1); no other casts

on type

boolean

 are allowed. A

boolean

 can be converted to a string by string

conversion ( 5.4).

4.3   Reference Types and Values

There are three kinds of

reference types

: class types ( 8), interface types ( 9), and

array types ( 10).

ReferenceType:

ClassOrInterfaceType

ArrayType

ClassOrInterfaceType:

ClassType

InterfaceType

ClassType:

TypeName

InterfaceType:

TypeName

ArrayType:

Type

 [ ]

Names are described in  6; type names in  6.5 and, specifically,  6.5.4.

37