private class implementing inner interface

I am trying to study this piece of code where private nested class implements a nested interface.

public class ConfigurationManager {

 private class ChainPowerListener implements PowerListener {

        private List<PowerListener> powerListeners = new CopyOnWriteArrayList<>();


        ChainPowerListener() {
            super();
        }

        public void registerListener(PowerListener listener) {
            powerListeners.add(listener);
        }

        @Override
        public void onAppPowerOn() {

        }

        @Override
        public void onAppPowerOff() {

        }
 }

}


public interface AppPower {

    boolean isPowerOn();

    void setPowerListener(PowerListener listener);

    public interface PowerListener {

        void onAppPowerOn();

        void onAppPowerOff();
    }

}

1. What does super refer to in the ChainPowerListener() constructor above? Is it the class that implements AppPower interface?
2. What is the benefit of this pattern if at all? Is this pattern common in Java world?

I am from c# background who is just starting to learn java. So hope you will be lenient if I am asking something stupid :)