Health care center class diagram to code

Classes found from the description: Patient, Physician, Scheduler, Appointment, Medication (holds the drug info: name, dosage amount, number of doses, refills), MedicalHistory, Prescription and Pharmacy. The "computer cross-check" is the hasConflict() method of Prescription, which checks each prescribed medication against the patient's current medications and medical history.

Class diagram

 +--------------------+ 1     * +-------------+ *     1 +--------------+
 |      Patient       |---------| Appointment |---------|  Physician   |
 |--------------------|         |-------------|         |--------------|
 | -name              |         | -date       |         | -name        |
 |--------------------|         | -cancelled  |         |--------------|
 | +getCurrentMeds()  |         |-------------|         | +prescribe() |
 | +getHistory()      |         | +cancel()   |         +--------------+
 +--------------------+         +-------------+                | 1
    | 1          | 1                   ^ creates/cancels       | writes
    | takes      | has                 |                       | *
    |            | 1            +-------------+        +-----------------+
    |    +-----------------+    |  Scheduler  |        |  Prescription   |
    |    | MedicalHistory  |    |-------------|        |-----------------|
    |    |-----------------|    | +arrange()  |        | -date           |
    |    | -conditions     |    | +cancel()   |        |-----------------|
    |    |-----------------|    +-------------+        | +hasConflict()  |
    |    | +conflictsWith()|    (Patient uses          | +forwardTo()    |
    |    +-----------------+     Scheduler)            | +print()        |
    | *                                                +-----------------+
    |                                                   | *       | *
 +-------------------+ 1..*       lists             |         | 0..1
 |    Medication     |----------------------------------+    +------------+
 |-------------------|                                       |  Pharmacy  |
 | -name             |                                       |------------|
 | -dosageAmount     |                                       | +receive() |
 | -numberOfDoses    |                                       +------------+
 | -refills          |
 +-------------------+

Code (Java)

import java.util.*;

class Medication {
    private String name; private double dosageAmount;
    private int numberDoses, refills;
    private Set<String> interactingDrugs = new HashSet<>();   // drug names
    private Set<String> contraindications = new HashSet<>();  // conditions/allergies
    public Medication(String n, double d, int doses, int refills) {
        name = n; dosageAmount = d; numberDoses = doses; this.refills = refills;
    }
    public String getName() { return name; }
    public void addInteraction(String drug) { interactingDrugs.add(drug); }
    public void addContraindication(String cond) { contraindications.add(cond); }
    public boolean interactsWith(Medication other) {
        return name.equalsIgnoreCase(other.name) || interactingDrugs.contains(other.name);
    }
    public boolean isContraindicatedFor(String condition) {
        return contraindications.contains(condition);
    }
}

class MedicalHistory {
    private List<String> conditions = new ArrayList<>();  // past illnesses, allergies
    public void addCondition(String c) { conditions.add(c); }
    public boolean conflictsWith(Medication m) {
        for (String c : conditions)
            if (m.isContraindicatedFor(c)) return true;
        return false;
    }
}

class Patient {
    private String name;
    private List<Medication> currentMedications = new ArrayList<>();
    private MedicalHistory history = new MedicalHistory();
    private List<Appointment> appointments = new ArrayList<>();
    public Patient(String name) { this.name = name; }
    public List<Medication> getCurrentMedications() { return currentMedications; }
    public MedicalHistory getHistory() { return history; }
    public void addAppointment(Appointment a) { appointments.add(a); }
    public void removeAppointment(Appointment a) { appointments.remove(a); }
}

class Appointment {
    private Date date; private Patient patient; private Physician physician;
    private boolean cancelled;
    public Appointment(Date d, Patient p, Physician ph) { date = d; patient = p; physician = ph; }
    public void cancel() { cancelled = true; }
}

class Scheduler {                     // used by the patient to arrange / cancel
    public Appointment arrange(Patient p, Physician ph, Date d) {
        Appointment a = new Appointment(d, p, ph);
        p.addAppointment(a);
        return a;
    }
    public void cancel(Patient p, Appointment a) { a.cancel(); p.removeAppointment(a); }
}

class Pharmacy {
    public void receive(Prescription rx) { System.out.println("Pharmacy got Rx"); }
}

class Prescription {
    private Date date = new Date();
    private Patient patient; private Physician physician;
    private List<Medication> medications = new ArrayList<>();
    public Prescription(Patient p, Physician ph) { patient = p; physician = ph; }
    public void add(Medication m) { medications.add(m); }

    public boolean hasConflict() {     // computer cross-check
        for (Medication m : medications) {
            for (Medication cur : patient.getCurrentMedications())   // current medications
                if (m.interactsWith(cur) || cur.interactsWith(m)) return true;
            if (patient.getHistory().conflictsWith(m)) return true; // medical history
        }
        return false;
    }
    public void forwardTo(Pharmacy ph) { ph.receive(this); }   // electronic
    public void print() { System.out.println("Prescription printed"); }
}

class Physician {
    private String name;
    public Physician(String n) { name = n; }
    public Prescription prescribe(Patient p, Medication m, Pharmacy ph) {
        Prescription rx = new Prescription(p, this);
        rx.add(m);
        if (rx.hasConflict()) { System.out.println("Conflict!"); return null; }
        if (ph != null) rx.forwardTo(ph); else rx.print();
        return rx;
    }
}

Associations were mapped to references and lists; the cross-check against current medications and medical history was mapped to hasConflict(); and the rule "forward electronically, or else print" was mapped to the if (ph != null) choice.