Alert Service

Refactor the AlertService and MapAlertDAO classes:

Create a new package-private interface, named AlertDAO, that contains the same methods as MapAlertDAO.
MapAlertDAO should implement the AlertDAO interface.
AlertService should have a constructor that accepts AlertDAO.
The raiseAlert and getAlertTime methods should use the object passed through the constructor.

Java SE 13

import java.util.Date;
import java.util.HashMap;
import java.util.Map;
import java.util.UUID;

class AlertService {
    private final MapAlertDAO storage = new MapAlertDAO();
		
    public UUID raiseAlert() {
        return this.storage.addAlert(new Date());
    }
	
    public Date getAlertTime(UUID id) {
        return this.storage.getAlert(id);
    }	
}

class MapAlertDAO {
    private final Map<UUID, Date> alerts = new HashMap<UUID, Date>();
	
    public UUID addAlert(Date time) {
    	UUID id = UUID.randomUUID();
        this.alerts.put(id, time);
        return id;
    }
	
    public Date getAlert(UUID id) {
        return this.alerts.get(id);
    }	
}

MapAlertDAO implements AlertDAO interface: Wrong answer
AlertService accepts AlertDAO in its constructor: Wrong answer
The raiseAlert and getAlertTime methods use AlertDAO passed through constructor: Wrong answer

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