doubt in protected access

[madhu v pe]

Hi I am having a doubt in protected access.
I wrote the code as below. some thing is missing can anyone help on this.

I am having 2 pacakges,
one defines protected variable
in another one I am accessing in subclass. in this scenario it should not give any error.
but it is thowing error

package pack1;
import java.awt.*;
 

public class pack1class
{
protected String prot="protected";
        protected void protMethod()
{
System.out.println("Protected Method");
}

}
 
class pack1subclass {
public static void main(String a[])
{
pack1class pc=new pack1class();
System.out.println("protected method"+pc.prot);
pc.protMethod();
}
}    

where it can be accessible without using reference to previous class since
it is inheriting.

package pack2;
import java.awt.*;
import pack1.*;
public class pack2subclassotherfile extends pack1class
{
public static void main(String[] sCommand)
{
System.out.println("protected method"+prot);
protMethod();
}
 
}    

Thanks in advance

[Sahid Khan]

what is the error you getting? is the classpath set properly?

[Pooja Jindal]

Well,
If you have Protected variables/Method in class pack1class.
and you are accessing it in subclass of pack1subclass (Please use Extends pack1class against it).
Then,
You can not access a Protected variable on Reference of the Super Class.
So,
pack1class pc=new pack1class();
System.out.println("protected method"+pc.prot); is Wrong!!

You should do it only through Inheritance.
like,replacing above code piece with this
System.out.println("protected method"+prot);



For More CClarifaication Refer to K& B Page no 35

[Manfred Klug]

Originally posted by madhu v pe:
Hi I am having a doubt in protected access.

Assuming that your classpath is correct, read the compiler message carefully. Your problem has nothing to do with protected access.

where it can be accessible without using reference to previous class since it is inheriting.

No, it's not inheriting. The reason that you don't get an error is that classes in the same package have the right to use members with default and protected access rights.

[Manfred Klug]

Originally posted by Pooja Jindal:
pack1class pc=new pack1class();
System.out.println("protected method"+pc.prot); is Wrong!!

There is no problem with this code, since both classes are in the same package. Have a look at the table on page 39.

[Himanshu Saxena]

Hi you are trying to use a non static field inside a static method.
static method can access only the static fields.
Learn about static ?



package pack2;
import java.awt.*;
import pack1.*;
public class pack2subclassotherfile extends pack1class
{
public static void main(String[] sCommand)
{
System.out.println("protected method"+prot);// not a static field
protMethod();
}

}

use this:

package pack2;
import java.awt.*;
import pack1.*;

public class pack2subclassotherfile extends pack1class{
String s=prot; //acess protected variable
public static void main(String[] sCommand)
{
pack2subclassotherfile a=new pack2subclassotherfile();
System.out.println("protected method"+a.prot);
a.protMethod();
}

}

[madhu v pe]

Hi all,
Thanks for your replies,sorry I didn't mention the error.
class path everything is ok.

Please read the topic Protected Details from K&B "Access Modifiers (objectives 1.3 and 1.4)
there is an example

package certification;
public class Parent{
protected int x=9;
}    

there is another package

package other;
import certification.Parent;
class child extends Parent
{
public void testIt{
System.out.println("x is"+x);//no problem child inherits x
}
}    

In the same way I wrote my own code
as below.

    package pack1;
import java.awt.*;
 

public class pack1class
{
protected String prot="protected";


protected void protMethod()
{
System.out.println("Protected Method");
}

}
 
class pack1subclass {
public static void main(String a[])
{
pack1class pc=new pack1class();
System.out.println("protected method"+pc.prot);
pc.protMethod();
}
}

which produced correct output

protected methodprotected

I wrote another set of code to use protected instance variable and method as below

package pack2;
import java.awt.*;
import pack1.*;
public class pack2subclassotherfile extends pack1class
{
public static void main(String[] sCommand)
{
System.out.println("protected method"+prot);
protMethod();
}
 
}

the output is
non-static variable prot cannot be referenced from a static context System.out.println("protected method"+prot);
non-static method protMethod() cannot be referenced from a static context protMethod();

what is fault in my code comarative to the book concept.

[madhu v pe]

Hi I have modified my second program as below

package pack2;
import java.awt.*;
import pack1.*;
class pack2subclassotherfile1 extends pack1class
{
public  void main1()
{
System.out.println("protected method"+prot);
}
 
}
 
public class pack2subclassotherfile
{
public static void main(String a[])
{
pack2subclassotherfile1 p=new pack2subclassotherfile1();
p.main1();
}
}    

now it is working fine.