5.2

Assignment Conversion

CONVERSIONS AND PROMOTIONS

If

S

 is an interface type:

N

If

T

 is a class type, then

T

 must be

Object

, or a compile time error occurs.

N

If

T

 is an interface type, then

T

 must be either the same interface as

S

 or a

superinterface of

S

, or a compile time error occurs.

N

If

T

 is an array type, then a compile time error occurs.

If

S

 is an array type

SC[]

, that is, an array of components of type

SC

:

N

If

T

 is a class type, then

T

 must be

Object

, or a compile time error occurs.

N

If

T

 is an interface type, then a compile time error occurs unless

T

 is the

interface type

Cloneable

, the only interface implemented by arrays.

N

If

T

 is an array type

TC[]

, that is, an array of components of type

TC

,

 then a

compile time error occurs unless one of the following is true:

O

TC

 and

SC

 are the same primitive type.

O

TC

 and

SC

 are both reference types and type

SC

 is assignable to

TC

,

 as

determined by a recursive application of these compile time rules for

assignability.

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

arrays.

The following test program illustrates assignment conversions on reference

values, but fails to compile because it violates the preceding rules, as described in

its comments. This example should be compared to the preceding one.

public class Point { int x, y; }

public interface Colorable { void setColor(int color); }

public class ColoredPoint extends Point implements Colorable

{

int color;

public void setColor(int color) { this.color = color; }

}

class Test {

public static void main(String[] args) {

Point p = new Point();

ColoredPoint cp = new ColoredPoint();

//

Okay because

ColoredPoint

 is a subclass of

Point

:

p = cp;

//

Okay because

ColoredPoint implements Colorable

:

Colorable c = cp;

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