How to get the class name of the subclass from a static method in the superclass?

[Philippe Desrosiers]

I have the following:

class Super{

    protected Class whatsMyClass(){
        return getClass();
    }
}

class Sub extends Super{

...

    public void someMethod(){
        System.out.println(whatsMyClass().getName());
    }
}

Needless to say, the example is drastically over-simplified, but basically, as-is, the whatsMyClass method returns the Subclass, which is what I want. But I also want to be able to specify the whatsMyClass method as static. Is there any way to do this?

[Ernest Friedman-Hill]

Nope. getClass() needs to be called on an object of the given class; a static method has no such object available.

Put another way: a static method can't determine "the class you called it on."

[Campbell Ritchie]

And a superclass has no notion about what subclasses have been created.

[Philippe Desrosiers]

Yeah, the closest I came was throwing an exception, then examining the StackTraceElement array for the throwing class, but even that gives the Superclass...

Oh well.

[Steve Luke]

Philippe Desrosiers wrote:Yeah, the closest I came was throwing an exception, then examining the StackTraceElement array for the throwing class, but even that gives the Superclass...

Oh well.

I can't think of a way to do it 'automatically' but you can do it with some method calls:

public abstract class ParentClass 
{
	private static Class<? extends ParentClass> myClass;
	
	protected static void setMyClass(Class<? extends ParentClass> clazz)
	{
		myClass = clazz;
	}
	
	public static Class<? extends ParentClass> getMyClass() 
	{
		return myClass;
	}
}

class ChildClass extends ParentClass
{
	static
	{
		setMyClass(ChildClass.class);
	}
}

Add some error checking to make sure the class was set and you at least have a starting point. Here would be an example of when it might be used:

package statics;

public abstract class ParentClass 
{
	private static Class<? extends ParentClass> myClass;
	
	protected static void setMyClass(Class<? extends ParentClass> clazz)
	{
		myClass = clazz;
	}
	
	public static Class<? extends ParentClass> getMyClass() 
	{
		return myClass;
	}
	
	public abstract void doSomeWork();
}

package statics;

public class ChildClass extends ParentClass 
{
	static
	{
		setMyClass(ChildClass.class);
	}
	
	public void doSomeWork()
	{
		System.out.println("I am Child's work!");
	}
}

package statics;

public class Runner {

	public static void main(String[] args) throws InstantiationException, IllegalAccessException, ClassNotFoundException 
	{
		Class.forName("statics.ChildClass");
		
		ParentClass instance = (ParentClass)(ParentClass.getMyClass().newInstance());
		instance.doSomeWork();
	}

}