Scenario Air Traffic Control oversees all the flight plans of the flights taking off from airports in their jurisdiction

[correctanswer]

Scenario Air Traffic Control oversees all
the flight plans of the flights taking off from airports in their
jurisdiction. A flight plan includes the call sign of the
airplane and a list of all of the points on a route, including the
departure and the destination airports, in the order in which they
should be encountered (these points are
called waypoints).

A Waypoint has a name, a coordinate and
an altitude.

The class Waypoint:
Please note that the answer box below
contains two classes to
complete. You can only use import statements at the
top of the answer box.
The answer box below includes some methods of the
class FlightPlan that you should not alter, as well as
the declarations for the fields of
the AirTrafficControl class.
(a) Develop only the class FlightPlan in this
part, which is already partially developed below.
(i) Add a declaration for a private instance variable
called route, which should be declared as
a ArrayList containing elements of
type Waypoint.
(ii) Add a public constructor
for FlightPlan that takes one string parameter
representing the call sign of the airplane and initialises the
related variable accordingly. The constructor should also
initialise route to a suitable empty
collection.
(iii) Add a standard getter method for
the route collection.
(iv) Write a public instance
method greatestAltitude that has no parameters and
returns the altitude of the highest waypoint on the route of this
flight plan. You can assume that there are at least three
waypoints on the route.
(v) Write a public instance
method destination that returns the name of the
final waypoint on the route of this flight
plan.
(vi) The air traffic controllers want to be able to sort
flight plans by their call signs in ascending order. Modify
the FlightPlan class so that it implements the
appropriate interface, and then implement
the compareTo method that will allow the ordering
required.
(b) Develop only the
class AirTrafficControl in this part, which is already
partially developed below.
(i) Add a public AirTrafficControl constructor
that initialises flightPlans to a suitable collection
type (initially empty).
(ii) Add a public method addFlightPlan that
adds the parameter, of
type FlightPlan to flightPlans. Nothing is returned
from the method.
(iii) Add a public instance
method routeMap that returns a HashMap in which
the keys are the call signs of the flight plans and each value is
an ArrayList of the names of the waypoints on the
corresponding route, in the order in which they should be
encountered.
My code so far:
//Scroll down to see the AirTrafficContol class below the
FlightPlan class
/**
* The class FlightPlan models a flight plan for an air
journey.
* Complete the class according to the instructions in part
(a)
*/

import java.util.*;
class FlightPlan
{
private String callSign;
/**
* Getter for the call sign of the aircraft
*/
public String getCallSign()
{
return callSign;
}
/**
* A simple equals method
*/
public boolean equals(Object o)
{
FlightPlan f = (FlightPlan) o;

return
getCallSign().equals(f.getCallSign());
}

/**
* return a hash code for this object based on its
call sign
*/
public int hashCode()
{
return callSign.hashCode();
}
}
/**
* This class models Air Traffic Control that oversees flight
plans.
* Complete this class according to the instructions in part
(b)
*/
class AirTrafficControl
{
public TreeSet<FlightPlan> flightPlans;
//public for testing purposes

public TreeSet<FlightPlan>
getFlightPlans()
{
return flightPlans;
}

// Add further code for the AirTrafficControl class
here

}