protected clone Java

manolakis · 11-10-2007, 09:20 AM

Hi all!!!
I am facing a problem with a the java.lang.object class.
I am actually trying to pass as a parameter in a method a Class and then clone() that object/class.
An example could be:

Quote:

public AObject doSmth(AObject obj)
{
...
AObject orig = (AObject) obj.clone();
return orig.clone();
}

public class AObject extends Object{}

You can notice that AObject class extends Object class. My problem is the following error:

Quote:

clone() has protected access in java.lang.Object
AObject orig = (AObject) obj.clone();

Any ideas how to overcome this problem?
Thanks

Alien_Hominid · 11-10-2007, 11:20 AM

Your class should implement cloneable interface.

ilikejam · 11-10-2007, 11:44 AM

Hi.

Do you get the error at runtime, or compiletime? The following compiles OK for me...

Code:

public class AObject extends Object{
    
    public AObject doSmth(AObject obj) throws CloneNotSupportedException
    {
	AObject orig = (AObject)obj.clone();
	return orig;
    }
    
}

Dave

jay73 · 11-10-2007, 12:33 PM

Put this in your AObject class

public Object clone() throws CloneNotSupportedException(){return super.clone();}

You also need to make sure that it implements Cloneable.

Alien_Hominid · 11-10-2007, 01:19 PM

Quote:

Originally Posted by ilikejam

Hi.

Do you get the error at runtime, or compiletime? The following compiles OK for me...

Code:

public class AObject extends Object{
    
    public AObject doSmth(AObject obj) throws CloneNotSupportedException
    {
	AObject orig = (AObject)obj.clone();
	return orig;
    }
    
}

Dave

You'll get CloneNotSupportedException, when you try to clone.

manolakis · 11-10-2007, 01:36 PM

Hi again and thanks everyone for your replies
The case is that AObject it is not my Class. I am trying to use a Java package. That was an example of my code. AObject is a class in that package that I want to return from a method. I tried to implement Cloneable in my Driver Class of the package but again I got the same error.
Any other ideas?

Thanks

manolakis · 11-10-2007, 03:42 PM

Will it easy for anyone to post how to use getClass() to compare two objects? Thanks

jay73 · 11-10-2007, 04:09 PM

class A{}

public class CheckClass {

public static void main (String [] args){

Long lng = new Long(10);
A a = new A();

System.out.println(lng.getClass()==Long.class);
System.out.println(a.getClass()==A.class);

}

}

Both return true.

manolakis · 11-10-2007, 05:48 PM

Many thanks

Alien_Hominid · 11-11-2007, 04:30 AM

Quote:

Originally Posted by manolakis

Hi again and thanks everyone for your replies
The case is that AObject it is not my Class. I am trying to use a Java package. That was an example of my code. AObject is a class in that package that I want to return from a method. I tried to implement Cloneable in my Driver Class of the package but again I got the same error.
Any other ideas?

Thanks

There are several problems:

1) You can't access protected method from separate class => solution: extend AObject class and override clone() method, get AObject clone using super.clone()

2) AObject should implement cloneable interface. If it doesn't, you can't clone it.

manolakis · 12-20-2007, 08:04 AM

Hi there

Does anybody know how to get the subclasses of a class, in particular in the following example:

Quote:

public class B extends A{...}

public class A{...}

public class C
{
public static void main(String [] args)
{
A a = new A();
Class b_class = a.getItsSubClass();
}
}

I would be really happy if anyone knows how to implement a method like getItsSubClass().

Thanks for your time