a very lengthy lab indeed!

interfaces-1.iml

@@ -0,0 +1,16 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<module org.jetbrains.idea.maven.project.MavenProjectsManager.isMavenModule="true" type="JAVA_MODULE" version="4">
+  <component name="NewModuleRootManager" LANGUAGE_LEVEL="JDK_1_5">
+    <output url="file://$MODULE_DIR$/target/classes" />
+    <output-test url="file://$MODULE_DIR$/target/test-classes" />
+    <content url="file://$MODULE_DIR$">
+      <sourceFolder url="file://$MODULE_DIR$/src/main/java" isTestSource="false" />
+      <sourceFolder url="file://$MODULE_DIR$/src/test/java" isTestSource="true" />
+      <excludeFolder url="file://$MODULE_DIR$/target" />
+    </content>
+    <orderEntry type="inheritedJdk" />
+    <orderEntry type="sourceFolder" forTests="false" />
+    <orderEntry type="library" scope="TEST" name="Maven: junit:junit:4.12" level="project" />
+    <orderEntry type="library" scope="TEST" name="Maven: org.hamcrest:hamcrest-core:1.3" level="project" />
+  </component>
+</module>

src/main/java/io/zipcoder/interfaces/Educator.java

@@ -0,0 +1,33 @@
+package io.zipcoder.interfaces;
+
+public enum Educator implements Teacher{
+    DOLIO (new Instructor(1l,"Dolio")),
+    LEON (new Instructor(2l,"Leon")),
+    KRIS (new Instructor(3l,"Kris"));
+
+    private final Instructor instructor;
+    private double timeWorked;
+
+    Educator(Instructor instructor) {
+        this.instructor=instructor;
+    }
+
+    public void teach(Learner learner, double numberOfHours) {
+        this.instructor.teach(learner,numberOfHours);
+        timeWorked+=numberOfHours;
+    }
+
+    public Instructor getInstructor() {
+        return instructor;
+    }
+
+    public void lecture(Learner[] learners, double numberOfHours) {
+        Students students=Students.getInstance();
+        this.instructor.lecture(learners,numberOfHours);
+        timeWorked+=numberOfHours/students.personList.size();
+    }
+
+    public double getTimeWorked() {
+        return timeWorked;
+    }
+}

src/main/java/io/zipcoder/interfaces/Instructor.java

@@ -0,0 +1,19 @@
+package io.zipcoder.interfaces;
+
+public class Instructor extends Person implements Teacher{
+
+    public Instructor(Long id, String name) {
+        super(id, name);
+    }
+
+    public void teach(Learner learner, double numberOfHours) {
+        learner.learn(numberOfHours);
+    }
+
+    public void lecture(Learner[] learners, double numberOfHours) {
+        double numberOfHoursPerLearner = numberOfHours / learners.length;
+        for (Learner learner : learners) {
+            learner.learn(numberOfHoursPerLearner);
+        }
+    }
+}

src/main/java/io/zipcoder/interfaces/Instructors.java

@@ -0,0 +1,17 @@
+package io.zipcoder.interfaces;
+
+public class Instructors extends People<Instructor>{
+    private static final Instructors instance=new Instructors();
+
+    private Instructors(){
+        this.add(new Instructor(1l,"Dolio"));
+        this.add(new Instructor(2l,"Leon"));
+        this.add(new Instructor(3l,"Kris"));
+    }
+
+    public static Instructors getInstance(){return instance;}
+
+    public Instructor[] getArray() {
+        return super.personList.toArray(new Instructor[0]);
+    }
+}

src/main/java/io/zipcoder/interfaces/Learner.java

@@ -0,0 +1,6 @@
+package io.zipcoder.interfaces;
+
+public interface Learner {
+    void learn(double numberOfHours);
+    Double getTotalStudyTime();
+}

src/main/java/io/zipcoder/interfaces/People.java

@@ -0,0 +1,53 @@
+package io.zipcoder.interfaces;
+
+import java.util.ArrayList;
+import java.util.Iterator;
+import java.util.List;
+
+public abstract class People<E extends Person> implements Iterable<E>{
+
+    List<E> personList = new ArrayList<E>();
+
+    public void add(E person) {
+        personList.add(person);
+    }
+
+    public E findByID(Long id) {
+        for (E person : personList)
+            if (person.getId() == (id))
+                return person;
+        return null;
+    }
+
+    public boolean contains(E person) {
+        if(personList.contains(person))
+            return true;
+        return false;
+    }
+
+    public void remove(E person) {
+        if(contains(person)) {
+            personList.remove(person);
+        }
+    }
+
+    public void removeById(Long id) {
+        E person = findByID(id);
+        remove(person);
+    }
+
+    public void removeAll() {
+        personList.clear();
+    }
+
+    public Integer count() {
+        return personList.size();
+    }
+
+    public abstract E[] getArray();
+
+    public Iterator<E> iterator() {
+        return personList.iterator();
+    }
+
+}