protected access type
Possible Duplicate:
In Java, what's the difference between public, default, protected, and private?
Why can't a subclass in one package access the protected member of it's superclass (in another package) by the reference of the superclass? I am struggling with this point. Please help me
package points;
public class Point {
protected int x, y;
}
package threePoint;
import points.Point;
public class Point3d extends Point {
protected int z;
public void delta(Point p) {
p.x += this.x; // compile-time error: cannot access p.x
p.y += this.y; // compile-time error: cannot access p.y
}
A protected member can be accessed by the class, other classes in the package and implicitly by its subclasses. ie, the subclass can access x from its own parent.
The fact that you are able to access this.x proves that x from the superclass is accessible. If x were private in the superclass, this.x would give an error.
When you say px you are trying to access some other instance's x , and not in its own hierarchy. This is not allowed outside the package.
Because you reference the members of a different instance of Point . This is not allowed.
You can of course access the inherited members as you do with this.x .
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