Java programming idiom : Private implementation class

I found this construct in some code.

Is there any benefit to have a private static class implement A? This reminded me of the Pimpl idiom in C++. Is there any benefit to using the Pimpl idiom in Java?

public abstract class A {
    public void doStuff();

    public static A getNewInstance() {
       return new AImpl();
    }

    private static class AImpl extends A {
        public void doStuff()  {
           ....
        }    
    } 

}