CONVERSIONS AND PROMOTIONS

Narrowing Reference Conversions

5.1.5

From any interface type to type

Object

.

From any array type to type

Object

.

From any array type to type

Cloneable

.

From any array type

SC[]

 to any array type

TC[]

, provided that

SC

 and

TC

are reference types and there is a widening conversion from

SC

 to

TC

.

Such conversions never require a special action at run time and therefore never

throw an exception at run time. They consist simply in regarding a reference as

having some other type in a manner that can be proved correct at compile time.

See  8 for the detailed specifications for classes,  9 for interfaces, and  10 for

arrays.

5.1.5   Narrowing Reference Conversions

The following conversions are called the

narrowing reference conversions

:

From any class type

S

 to any class type

T

, provided that

S

 is a superclass of

T

.

(An important special case is that there is a narrowing conversion from the

class type

Object

 to any other class type.)

From any class type

S

 to any interface type

K

, provided that

S

 is not final and

does not implement

K.

 (An important special case is that there is a narrowing

conversion from the class type

Object

 to any interface type.)

From type

Object

 to any array type.

From type

Object

 to any interface type.

From any interface type

J

 to any class type

T

 that is not

final

.

From any interface type

J

 to any class type

T

 that is

final

, provided that

T

implements

J

.

From any interface type

J

 to any interface type

K

, provided that

J

 is not a sub 

interface of

K

 and there is no method name

m

 such that

J

 and

K

 both declare a

method named

m

 with the same signature but different return types.

From any array type

SC[]

 to any array type

TC[]

, provided that

SC

 and

TC

are reference types and there is a narrowing conversion from

SC

 to

TC

.

Such conversions require a test at run time to find out whether the actual reference

value is a legitimate value of the new type. If not, then a

ClassCastException

 is

thrown.

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