Question

I have the following classes.

public class Super{

  public static void useSubClass(){
     //I want to access the sub class object here, how.
  }
}

public class Sub1 extends Super{

}

public class Sub2 extends Super{

}

I want to access the sub-class object from a static method in super-class. i.e. When I call Sub1.useSubClass() the method has access to Sub1.class and when I use Sub2.useSubClass(), I can access the Sub2.class.

Is there any way to access the sub-class object from super-class.

Answer 1

I figured something out. It works if implemented with care.

/** SuperClass.java **/
public abstract class SuperClass {

    public static void printClass(){
    System.out.println(new ImplementingClassRetriever().getCallingClass());
    }

    static class ImplementingClassRetriever extends SecurityManager{
    public Class getCallingClass() {
        Class[] classes = getClassContext();
        for (Class clazz : classes) {
        if (SuperClass.class.isAssignableFrom(clazz) && clazz != null
            && !clazz.equals(SuperClass.class)) {
            return clazz;
        }
        }
        return null;
    }
    }
}


/** Main.java **/
public class Main{
    public static void main(String[] args) {
    Sub.printClass(); //this does not work
    Sub.testStaticCall(); //this works!! :)
    }
}


class Sub extends SuperClass{

    public static void testStaticCall(){
    Sub.printClass(); //calling the method in the super class
    }
}

This is just a toy example. The super class contains a static class that contains a method to retrieve the calling class.

In the subclass I have another static method which calls the superclass’s method for printing the class name.

The Main class/function contains two calls to Sub‘s inherited and locally implemented method. The first call prints null, because the calling context (i.e. Main) is not a subclass of Super However the delegate method in Sub works because the calling context is now a subclass of SuperClass and hence the calling class can be determined.