8.3.3

Examples of Field Declarations

CLASSES

class Point {

int x = 2;

}

class Test extends Point {

double x = 4.7;

void printBoth() {

System.out.println(x + " " + super.x);

}

public static void main(String[] args) {

Test sample = new Test();

sample.printBoth();

System.out.println(sample.x + " " +

((Point)sample).x);

}

}

produces the output:

4.7 2

4.7 2

because the declaration of

x

 in class

Test

 hides the definition of

x

 in class

Point

,

so class

Test

 does not inherit the field

x

 from its superclass

Point

. It must be

noted, however, that while the field

x

 of class

Point

 is not

inherited

 by class

Test

, it is nevertheless

implemented

 by instances of class

Test

. In other words,

every instance of class

Test

 contains two fields, one of type

int

 and one of type

float

. Both fields bear the name

x

, but within the declaration of class

Test

, the

simple name

x

 always refers to the field declared within class

Test

. Code in

instance methods of class

Test

 may refer to the instance variable

x

 of class

Point

as

super.x

.

Code that uses a field access expression to access field

x

 will access the field

named

x

 in the class indicated by the type of reference expression. Thus, the

expression

sample.x

 accesses a

float

 value, the instance variable declared in

class

Test

, because the type of the variable sample is

Test

, but the expression

((Point)sample).x

 accesses an

int

 value, the instance variable declared in

class

Point

, because of the cast to type

Point

.

If the declaration of

x

 is deleted from class

Test

, as in the program:

class Point {

static int x = 2;

}

class Test extends Point {

void printBoth() {

System.out.println(x + " " + super.x);

}

public static void main(String[] args) {

Test sample = new Test();

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