4.1

The Kinds of Types and Values

TYPES, VALUES, AND VARIABLES

of type  array of

T

 ; if

T

 is a reference type, then a variable of type  array of

T

can hold a null reference or a reference to any array of type  array of

S

  such that

type

S

 is assignable ( 5.2) to type

T

. A variable of type

Object

 can hold a null

reference or a reference to any object, whether class instance or array.

4.1   The Kinds of Types and Values

There are two kinds of

types

 in Java: primitive types ( 4.2) and reference types

( 4.3). There are, correspondingly, two kinds of data values that can be stored in

variables, passed as arguments, returned by methods, and operated on: primitive

values ( 4.2) and reference values ( 4.3).

Type:

PrimitiveType

ReferenceType

There is also a special

null type

, the type of the expression

null

, which has no

name. Because the null type has no name, it is impossible to declare a variable of

the null type or to cast to the null type. The null reference is the only possible

value of an expression of null type. The null reference can always be cast to any

reference type. In practice, the Java programmer can ignore the null type and just

pretend that

null

 is merely a special literal that can be of any reference type.

4.2   Primitive Types and Values

A

primitive type

 is predefined by the Java language and named by its reserved

keyword ( 3.9):

PrimitiveType:

NumericType

boolean

NumericType:

IntegralType

FloatingPointType

IntegralType: one of

byte short int long char

FloatingPointType: one of

float double

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