src/main/java/lecture5/objects/Book.java

+package lecture5.objects;
+
+public class Book {
+
+    String title;
+    String author;
+
+    public Book(String title, String author){
+        this.title = title;
+        this.author = author;        
+    }
+
+    public String toString(){
+        return String.format("%s - %s", this.title, this.author);
+    }
+
+    public boolean equals(Object obj){
+        
+    }
+    
+}

src/main/java/lecture5/objects/Library.java

+package lecture5.objects;
+
+import java.util.ArrayList;
+
+public class Library {
+    
+    ArrayList<Book> books;
+
+    public Library(){
+
+        books = new ArrayList<Book>();
+
+    }
+
+    void add(Book book){
+        books.add(book);
+
+    }
+
+    boolean hasBook(Book book){
+        return books.contains(book);
+    }
+
+    public static void main(String[] args){
+
+        Library myBooks = new Library();
+        System.out.println(myBooks.books);
+
+        myBooks.add(new Book("Hvordan være tøff", "Anders"));
+
+        System.out.println(myBooks.books);
+
+        Book myFavorite = new Book("INF101", "Sondre");
+
+        System.out.println(myBooks.hasBook(myFavorite));
+
+        myBooks.add(myFavorite);
+
+        System.out.println(myBooks.hasBook(myFavorite));
+
+        System.out.println(myBooks.books);
+
+        Book wanted = new Book("Hvordan være tøff", "Anders");
+        System.out.println(myBooks.hasBook(wanted));
+
+    }
+
+    
+}

src/main/java/lecture5/objects/Persons.java

@@ -33,7 +33,7 @@ public class Persons {
 	 */
 	private static void removeLast(ArrayList<String> names, ArrayList<Integer> ages) {
 		names.remove(names.size()-1);
-		ages.remove(names.size()-1);
+		ages.remove(ages.size()-1);
 	}
 
 	/**

src/main/java/lecture5/objects/PersonsObjects.java

+package lecture5.objects;
+import java.util.ArrayList;
+
+
+
+/**
+ * This program keeps track of a list of persons names and ages.
+ * 
+ * @author Martin Vatshelle
+ */
+public class PersonsObjects {
+
+	public static void main(String[] args) {
+		ArrayList<Person> persons = new ArrayList<Person>();
+		
+		fill(persons);
+		printAll(persons);
+		removeLast(persons);
+		System.out.println();
+		printAll(persons);
+	}
+
+	/**
+	 * Persons are stored in 2 lists, 
+	 * index i in names gives the name of person i and 
+	 * index i in ages gives the age of person i
+	 * 
+	 * This method removes the last person from the list
+	 * 
+	 * @param names a list of names
+	 * @param ages a list of ages
+	 */
+	private static void removeLast(ArrayList<Person> persons) {
+		persons.remove(persons.size()-1);
+	}
+
+	/**
+	 * Fills two lists with the same number of elements.
+	 * names.get(i) and ages.get(i) are the name and age of person i
+	 *  
+	 * @param names The List of names to be filled
+	 * @param ages The List of ages to be filled
+	 */
+	public static void fill(ArrayList<Person> persons) {
+
+		persons.add(new Person("Anna", 12));
+		persons.add(new Person("Per", 3));
+		persons.add(new Person("Hans", 7));
+		persons.add(new Person("Lise", 9));
+
+	}
+	
+	/**
+	 * Prints out the names and ages of a list of Persons
+	 * 
+	 * @param names
+	 * @param ages
+	 */
+	public static void printAll(ArrayList<Person> persons) {
+		for(int i=0; i<persons.size(); i++) {
+			Person p = persons.get(i);
+			// System.out.println(p.name +" is "+ p.age +" years.");
+			System.out.println(p);
+		}
+	}
+}