Initial commit

.gitignore

+/.classpath
+/.project
+/.settings
+/bin

src/java_exercises3_1_1/Alumni.java

+package java_exercises3_1_1;
+
+/**
+ * Alumnis are graduated students, which may also attend courses.
+ * @author mad
+ *
+ */
+public class Alumni implements Attendee {
+	private String name;
+	
+	
+	public Alumni(String name) {
+		super();
+		this.name = name;
+	}
+	
+	/**
+	 * Implementation of getName defined in the Attendee interface.
+	 */
+	public String getName() {
+		// TODO Auto-generated method stub
+		return this.name;
+	}
+
+}

src/java_exercises3_1_1/Attendee.java

+package java_exercises3_1_1;
+
+/**
+ * An Attendee just has a name nothing more.
+ * @author mad
+ *
+ */
+public interface Attendee {
+	public String getName();
+}

src/java_exercises3_1_1/CircleFactory.java

+package java_exercises3_1_1;
+
+public class CircleFactory {
+	public static void main(String[] args) {
+	
+	}
+
+}

src/java_exercises3_1_1/Course.java

+package java_exercises3_1_1;
+
+/**
+ * The class Course represents a university course. There are special courses like Webinar which are
+ * represented in subclasses. 
+ * @author mad
+ *
+ */
+public class Course {
+	private String name;
+	private int id;
+	
+	public Course(String name, int id) {
+		this.name=name;
+		this.id=id;
+	}
+
+	public String getName() {
+		return name;
+	}
+
+	public int getId() {
+		return id;
+	}
+	
+	/**
+	 * Method to book course by an Attendee. As Attendee is only an interface it could actually be a student or an alumni. But this fact is not known by
+	 * the class Course. This is good because this way also other classes could implement interface Attendee without a having to change the code of class Course.
+	 * @param attendee
+	 */
+	public void book(Attendee attendee) {
+		System.out.println("The attendee <"+attendee.getName()+"> is booked  for the course <"+getName()+">");
+	}
+
+	/**
+	 * Overrides the toString method of the root superclass Object.
+	 * Returns a concatenated string containing the values of the member variables.
+	 * Is automatically called when a reference variable is used in a System.out.println method.
+	 */
+	public String toString() {
+		return "Course [name=" + name + ", id=" + id + "]";
+	}
+	
+	
+}

src/java_exercises3_1_1/LabCourse.java

+package java_exercises3_1_1;
+
+import java.util.Arrays;
+
+/**
+ * This class represents a special course with laboratories. It inherits some methods from Course.
+ * @author mad
+ *
+ */
+public class LabCourse extends Course {
+	private String[] exercises=new String[0];
+	
+	public LabCourse(String name, int id, String[] exercises) {
+		//Use the ctor of Course to init the vars name and id.
+		super(name, id);
+		this.exercises=exercises;
+	}
+
+	/**
+	 * Returns the exercises of the lab.
+	 * @return
+	 */
+	public String[] getExercises() {
+		return exercises;
+	}
+
+	/**
+	 * Override method toString to also add the exercises contents to the string.
+	 */
+	public String toString() {
+		return "LabCourse [exercises=" + (exercises != null ? Arrays.asList(exercises) : null) + ", toString()="
+				+ super.toString() + "]";
+	}
+	
+	
+	//All other methods are inherited.
+}

src/java_exercises3_1_1/Student.java

+package java_exercises3_1_1;
+
+/**
+ * A student implements Attendee, because he/she is allowed to attend courses.
+ * @author mad
+ *
+ */
+public class Student implements Attendee {
+	private String name;
+	private int id;
+	private int[] grades;
+	
+	
+	public Student(String name, int id) {
+		super();
+		this.name = name;
+		this.id = id;
+	}
+	
+	/**
+	 * Implementation of getName defined in the Attendee interface.
+	 */
+
+	public String getName() {
+		return name;
+	}
+	public int[] getGrades() {
+		return grades;
+	}
+	public void setGrades(int[] grades) {
+		this.grades = grades;
+	}
+	public int getId() {
+		return id;
+	}
+}

src/java_exercises3_1_1/TestUni.java

+package java_exercises3_1_1;
+
+import java_exercises3_1_1.*;
+
+/**
+ * Test the behaviour of the university example.
+ * @author mad
+ *
+ */
+public class TestUni {
+	public static void main(String[] args) {
+		//Instantiate student called Martin
+		Student student=new Student("Martin",1);
+		University uni=new University();
+		//Register student
+		uni.register(student);
+		
+		//Book Student Martin for the course Java Intro
+		Course course=new Course("Java Intro",1);
+		//From here we can't access the member variables of class Course because they are private.
+		//Let's try to book the course by a Student.
+		course.book(student);
+		
+		//Book Alumni Peter for course Java Intro
+		Alumni alumni=new Alumni("Peter");
+		//Also alumnis are allowed to book a course.
+		course.book(alumni);
+		//But alumnis are not allowed to register. If you uncomment the follwing line you will get a compile error.
+		//uni.register(alumni);
+		
+		//Both alumnis and students implement the Attendee interface and hence provide a method called getName.
+		System.out.println("Name of Student: "+student.getName()+", Name of Alumni: "+alumni.getName());
+
+	}
+}

src/java_exercises3_1_1/University.java

+package java_exercises3_1_1;
+
+import java.util.Arrays;
+
+/**
+ * The class university manages students studying there.
+ * @author mad
+ *
+ */
+public class University {
+	public Student[] students=new Student[0];
+	
+	public void register(Student student) {		
+		/**students is an array of class Student, so we have to allocate a new size first.
+		   Then we copy previously registered students to the new array instance.
+		   Generally for this task Java collections like {@link Map} or {@link List} would be much better and will
+		   be topic in a later session.
+		 */	
+		students=(Student[]) Arrays.copyOf(students, students.length+1);
+		students[students.length-1]=student;
+		System.out.println("Registerd student: "+student.getId()+": "+student.getName()+", new array size: "+students.length);
+	}
+	
+	public void deregister(Student student) {
+		for(int i=0; i<students.length;i++) {
+			if(students[i].getId()==student.getId()) {
+				students[i]=null;
+				System.out.println("Deregisterd student: "+student.getId()+": "+student.getName()+", new array size: "+students.length);
+				break;
+			}
+		}
+	}
+
+}

src/java_exercises3_1_1/Webinar.java

+package java_exercises3_1_1;
+
+import java.net.URL;
+
+/**
+ * This class represents webinar courses.
+ * @author mad
+ *
+ */
+public class Webinar extends Course {
+	private URL webinarURL;
+	
+	/**
+	 * ctor of a webinar with the name, id and URL parameters.
+	 * @param name
+	 * @param id
+	 * @param webinarURL
+	 */
+	public Webinar(String name, int id, URL webinarURL) {
+		super(name, id);
+		this.webinarURL=webinarURL;
+	}
+
+	/**
+	 * Returns the webinar URL.
+	 * @return
+	 */
+	public URL getWebinarURL() {
+		return webinarURL;
+	}
+
+	/**
+	 * Override method toString to also add the webinarURL to the string.
+	 */
+	public String toString() {
+		return "Webinar [webinarURL=" + webinarURL + ", toString()=" + super.toString() + "]";
+	}
+}