Inheriting Protected Variables

[Santiago Bravo]

Hi, this is a SCJP1.5 tip from Devesh Chanchlani's site:

http://devesh2k1.googlepages.com/home

The following wont compile:

package p1;
public class A {
protected int i = 10;
public int getI() { return i; }
}

package p2;
public class B extends p1.A {
public void process(A a)
{ a.i = a.i*2; }
public static void main(String[] args)
{
A a = new B();
B b = new B();
b.process(a);
System.out.println( a.getI() );
}
}


The reason given is that the variable 'i' is protected and B cannot access it. If the process method was defined as void process(B b){ b.i....etc then it will work.

My questions are:

1. Where will this error occur? On the creation of the method process (A a) or when it it called in the main method - b.process(a); ?
2. Can protected variables only be accessed in a subclass in another package using the instance of the class (i.e. B)?
3. Is Qs 2 the same for protected methods?


Thanks

[Paul Campbell]

Originally posted by Santiago Bravo:

My questions are:

1. Where will this error occur? On the creation of the method process (A a) or when it it called in the main method - b.process(a); ?
2. Can protected variables only be accessed in a subclass in another package using the instance of the class (i.e. B)?
3. Is Qs 2 the same for protected methods?


Thanks

1) EDIT: I answered your first question too quickly... i.e., I should of read it before my fingers did their typing... the error will be here:
{ a.i = a.i*2; } my apologies... i realized my error in the first mile of my after work run.

2) Protected members are accessible as either through inheritence or being part of the same package.

3) Yes
[ October 08, 2008: Message edited by: Paul Campbell ]

[Sandhya Bhaskara]

package p1;
public class A {
protected int i = 10;
public int getI() { return i; }
}
 
package p2;
public class B extends p1.A {
public void process([B]A [/B]a)
{ a.i = a.i*2; }
public static void main(String[] args)
{
[B]A[/B] a = new B();
B b = new B();
b.process(a);
System.out.println( a.getI() );
}
 
}

shouldn't this be p1.A since we did not import A

[Ankit Garg]

Nice observation Sandhya...

[Santiago Bravo]

Thanks Paul. It makes sense now