      class Employees { 
                            private List&lt;Person&gt; employees;
                            bool hire(Person p) { employees.add(p); }
                            bool fire(Person p) { employees.remove(p); }
                            bool isEmplyee(Person p) { employee.contains(p); }
                        }
                            </code></pre>
                </section>
    
            <section>
                <h1>Information hiding: Java Beispiel</h1>
                <p