public interface Monitor { public void update(String state); } // Subject Interface public interface GrassCuttingMachine { public void register(Monitor monitor); public void unregister(Monitor monitor); public void notifyObservers(String state); } // Simple Monitor public class SimpleMonitor implements Monitor { @Override public void update(String state){ System.out.println("Simple Monitor: The grass-cutting machine needs repair: " + state); } } // Medium Monitor public class MediumMonitor implements Monitor { @Override public void update(String state){ System.out.println("Medium Monitor: The grass-cutting machine needs repair: " + state); } } // Advanced Monitor public class AdvancedMonitor implements Monitor { @Override public void update(String state){ System.out.println("Advanced Monitor: The grass-cutting machine needs repair: " + state); } } // Concrete Subject public class CuttingMachine implements GrassCuttingMachine { private List monitors = new ArrayList<>(); @Override public void register(Monitor monitor) { monitors.add(monitor); } @Override public void unregister(Monitor monitor) { monitors.remove(monitor); } @Override public void notifyObservers(String state) { for (Monitor monitor : monitors) { monitor.update(state); } } } // Client public class Main { public static void main(String[] args) { GrassCuttingMachine grassCuttingMachine = new CuttingMachine(); SimpleMonitor simpleMonitor = new SimpleMonitor(); grassCuttingMachine.register(simpleMonitor); grassCuttingMachine.notifyObservers("WORKING-NORMALLY"); grassCuttingMachine.notifyObservers("MINOR-REPAIR-NEEDED"); MediumMonitor mediumMonitor = new MediumMonitor(); grassCuttingMachine.register(mediumMonitor); grassCuttingMachine.notifyObservers("MAJOR-REPAIR-NEEDED"); grassCuttingMachine.notifyObservers("HARD-TO-FIX"); AdvancedMonitor advancedMonitor = new AdvancedMonitor(); grassCuttingMachine.register(advancedMonitor); grassCuttingMachine.notifyObservers("TOTALLY-BROKEN"); } }

Please draw UML class diagram for the above code