Why declare the class that you included as a header file?
<p>Why declare the class that you included as a header file? </p>

<pre><code>#include "TreeCallObj.h"
#include "TreeDevObj.h"
#include "TreeDevCallObj.h"

class TreeCallObj; //what is the purpose of this line ?
class TreeDevObj;  //what is the purpose of this line ?
class TreeDevCallObj;  //what is the purpose of this line ?


class Apple
{
public:
...
private:
...
}
</code></pre>
