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Final Exam E03 Handout
for
e03
CS56 F17

Code for Amazany question

Product.java

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/** something that can be sold */
public abstract class Product {
    
    /** get the price (in cents) */
    public abstract int getPrice();
    
}

Shippable.java

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/** something that can be shipped */
public interface Shippable {
    /** get the shipping weight in pounds */
    public double getWeight();
}

Book.java

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/** A Book */
public class Book extends Product implements Shippable {

    private int price;
    private double weight;
    private String author;
    private String title;

    public Book(String author, String title, int price,
                double weight) {
        this.author = author;
        this.title = title;
        this.price = price;
        this.weight = weight;
    }

    public int getPrice() {return this.price;}
    public String getTitle() {return this.title;}
    public String getAuthor() {return this.author;}
    public double getWeight() {return this.weight;}
}

Song.java

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/** A downloadable Song */
public class Song extends Product {

    private int price;
    private String artist;
    private String title;

    public Song(String artist, String title, int price) {
        this.artist = artist;
        this.title = title;
        this.price = price;
    }

    public Song(String artist, String title) {
        this(artist,title,99);
    }

    public int getPrice() {return this.price;}
    public String getTitle() {return this.title;}
    public String getArtist() {return this.artist;}

}

 

Dog.java

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public class Dog {

    private static Dog dogOfTheWeek = null;
    private String name;

    public void setAsDogOfTheWeek() {
	dogOfTheWeek = this;
    }

    public static void resetDogOfTheWeek() {
	dogOfTheWeek = null;
    }

    public static Dog getDogOfTheWeek() {
	return dogOfTheWeek;
    }

    public Dog(String name) { this.name = name;}

    public static void main(String [] args) {

	Dog d1 = new Dog("Fido");
	Dog d2 = new Dog("Princess");
	Dog d3 = new Dog("Rover");
	Dog d4 = new Dog("Snoopy");
	Dog d5 = new Dog("Spot");
	Dog d6 = d4;
	
	d3.setAsDogOfTheWeek();  gc();    
	d2 = d4;                 gc();                   
	Dog temp = d1;           gc();             
	d1 = d6;                 gc();                   
	d5 = temp;               gc();                 
	d2 = getDogOfTheWeek();  gc();    
	d1.setAsDogOfTheWeek();  gc();    
	d6 = null;               gc();
        d5 = null;               gc();			
	d4 = null;               gc();                 
	d3 = null;               gc();                 
	d2 = null;               gc();                 
	d1 = null;               gc();                 
	temp = null;             gc();
	resetDogOfTheWeek();     gc();
    }                              

    public static void gc() {
       // ... encourage garbage collection
    }
}

class java.util.ArrayList<E>

The following excerpts from the javadoc for java.util.ArrayList<E> may be helpful to you in completing this exam.

Inheritance Hierarchy (complete)

java.lang.Object
  java.util.AbstractCollection<E>
    java.util.AbstractList<E>
      java.util.ArrayList<E>
All Implemented Interfaces: Serializable, Cloneable, Iterable<E>, Collection<E>, List<E>, RandomAccess
Direct Known Subclasses: AttributeList, RoleList, RoleUnresolvedList

Constructors (complete)

ArrayList() Constructs an empty list with an initial capacity of ten.
ArrayList(Collection<? extends E> c) Constructs a list containing the elements of the specified collection,
in the order they are returned by the collection’s iterator.
ArrayList(int initialCapacity) Constructs an empty list with the specified initial capacity.

Most important methods, with brief description

boolean add(E e) Appends the specified element to the end of this list.
void add(int index, E element) Inserts the specified element at the specified position in this list.
void clear() Removes all of the elements from this list.
E get(int index) Returns the element at the specified position in this list.
int indexOf(Object o) Returns the index of the first occurrence of the specified element in this list,
or -1 if this list does not contain the element.
boolean isEmpty() Returns true if this list contains no elements.
int lastIndexOf(Object o) Returns the index of the last occurrence of the specified element in this list,
or -1 if this list does not contain the element.
E remove(int index) Removes the element at the specified position in this list.
boolean remove(Object o) Removes the first occurrence of the specified element from this list, if it is present.
E set(int index, E element) Replaces the element at the specified position in this list with the specified element.
int size() Returns the number of elements in this list.
void sort(Comparator<? super E> c) Sorts this list according to the order induced by the specified Comparator.

Additional methods, listed by method signature only.

boolean addAll(Collection<? extends E> c) boolean addAll(int index, Collection<? extends E> c)
Object clone() boolean contains(Object o)
void ensureCapacity(int minCapacity) void forEach(Consumer<? super E> action)
Iterator<E> iterator() ListIterator<E> listIterator()
ListIterator<E> listIterator(int index) boolean removeAll(Collection<?> c)
boolean removeIf(Predicate<? super E> filter) protected void removeRange(int fromIndex, int toIndex)
void replaceAll(UnaryOperator<E> operator) boolean retainAll(Collection<?> c)
Spliterator<E> spliterator() List<E> subList(int fromIndex, int toIndex)
Object[] toArray() <T> T[] toArray(T[] a)
void trimToSize()  

Methods inherited from:

class java.util.AbstractList equals, hashCode
class java.util.AbstractCollection containsAll, toString
class java.lang.Object finalize, getClass, notify, notifyAll, wait, wait, wait
interface java.util.List containsAll, equals, hashCode
interface java.util.Collection parallelStream, stream

 

Hints for .equals()

As a reminder, a properly written overridden .equals() method:

  • Takes an Object o as its parameter
  • Returns a boolean value
  • Checks each of the following conditions, and for each, returns an appropriate result:
    • Does o refer to the same object as the one on which the .equals method was invoked?
    • Is o a null reference?
    • If o an instance of some other class, i.e. getClass() != o.getClass()
    • Typecasts o to an instance of the current class, and then compares values appropriately.
End of Handout