package Question10_2; import java.util.HashMap; public class Server { HashMap machines = new HashMap(); HashMap personToMachineMap = new HashMap(); public Machine getMachineWithId(int machineID) { return machines.get(machineID); } public int getMachineIDForUser(int personID) { Integer machineID = personToMachineMap.get(personID); return machineID == null ? -1 : machineID; } public Person getPersonWithID(int personID) { Integer machineID = personToMachineMap.get(personID); if (machineID == null) { return null; } Machine machine = getMachineWithId(machineID); if (machine == null) { return null; } return machine.getPersonWithID(personID); } }