15.10.1

Field Access Using a Primary

EXPRESSIONS

15.10.1   Field Access Using a Primary

The type of the

Primary

 must be a reference type

T

, or a compile time error

occurs. The meaning of the field access expression is determined as follows:

If the identifier names several accessible member fields of type

T

, then the

field access is ambiguous and a compile time error occurs.

If the identifier does not name an accessible member field of type

T

, then the

field access is undefined and a compile time error occurs.

Otherwise, the identifier names a single accessible member field of type

T

 and

the type of the field access expression is the declared type of the field. At run

time, the result of the field access expression is computed as follows:

N

If the field is

static

:

O

If the field is

final

, then the result is the value of the specified class vari 

able in the class or interface that is the type of the

Primary

 expression.

O

If the field is not

final

, then the result is a variable, namely, the specified

class variable in the class that is the type of the

Primary

 expression.

N

If the field is not

static

:

O

If the value of the

Primary

 is

null

, then a

NullPointerException

 is

thrown.

O

If the field is

final

, then the result is the value of the specified instance

variable in the object referenced by the value of the

Primary

.

O

If the field is not

final

, then the result is a variable, namely, the specified

instance variable in the object referenced by the value of the

Primary

.

Note, specifically, that only the type of the

Primary

 expression, not the class of the

actual object referred to at run time, is used in determining which field to use.

Thus, the example:

class S { int x = 0; }

class T extends S { int x = 1; }

class Test {

public static void main(String[] args) {

T t = new T();

System.out.println("t.x=" + t.x + when("t", t));

S s = new S();

System.out.println("s.x=" + s.x + when("s", s));

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