The Java Language Specification, Third Edition

CLASSES Examples of Field Declarations 8.3.3
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 double 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();
sample.printBoth();
System.out.println(sample.x + " " +
((Point)sample).x);
}
}
then the field x of class Point is no longer hidden within class Test. Within
instance methods in the declaration of class Test, the simple name x now refers to
the field declared within class Point. Code in class Test may still refer to that
same field as super.x. The expression sample.x still refers to the field x within
type Test, but that field is now an inherited field, and so refers to the field x
declared in class Point. The output from this variant program is:
2 2
2 2
DRAFT
8.3.3.3 Example: Multiply Inherited Fields
A class may inherit two or more fields with the same name, either from two interfaces
or from its superclass and an interface. A compile-time error occurs on any
attempt to refer to any ambiguously inherited field by its simple name. A qualified
name or a field access expression that contains the keyword super (§15.11.2) may
be used to access such fields unambiguously. In the example:
interface Frob { float v = 2.0f; }
class SuperTest { int v = 3; }
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