Names - The Java Language Specification - page 154

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package points;
public class Point {
public int x, y;
void move(int dx, int dy) { x += dx; y += dy; }
public void moveAlso(int dx, int dy) { move(dx, dy); }
}
then a subclass in another package may declare an unrelated move method, with the
same signature (§ 8.4.2 ) and return type. Because the original move method is not ac-
cessible from package morepoints , super may not be used:
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package morepoints;
public class PlusPoint extends points.Point {
public void move(int dx, int dy) {
super.move(dx, dy); // compile-time error
moveAlso(dx, dy);
}
}
Because move of Point is not overridden by move in PlusPoint , the method moveAlso in
Point never calls the method move in PlusPoint . Thus if you delete the super.move call
from PlusPoint and execute the test program:
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import points.Point;
import morepoints.PlusPoint;
class Test {
public static void main(String[] args) {
PlusPoint pp = new PlusPoint();
pp.move(1, 1);
}
}
it terminates normally. If move of Point were overridden by move in PlusPoint , then this
program would recurse infinitely, until a StackOverflowError occurred.
Example 6.6-5. Access to private Fields, Methods, and Constructors
A private class member or constructor is accessible only within the body of the top
level class (§ 7.6 ) that encloses the declaration of the member or constructor. It is not
inherited by subclasses. In the example: