Description
CSE 241/505
Object Oriented Programming
Fall 2018
Homework # 8
Generics and Collections in Java
Due date Jan 20rd 2019 (No late submission for this HW)
As we discussed in the lectures, Java has a very structured Collections library. We can develop a
similar simplified library for Java that uses arrays underneath. We will implement some the interfaces
some abstract class, some concrete classes, and some of the helper classes such as iterators.
The above figure shows a simplified version of the Collections. We will write corresponding generic
classes for Collection, Set, List, Queue, which are all interfaces. HashSet, ArrayList, and LinkedList
are concrete classes. Note that LinkedList uses multiple inheritance. Following table defines the
functions for each class
Class Name Public Method Name Definition
Collection This is a generic class with one generic parameters which is the generic type E.
iterator()
Returns an iterator over the collection
add(E e)
Ensures that this collection contains the specified element
addAll(Collection c)
Adds all of the elements in the specified collection to this
collection
clear()
Removes all of the elements from this collection
contains(E e)
Returns true if this collection contains the specified element.
containsAll(Collection c)
Returns true if this collection contains all of the elements in the
specified collection.
isEmpty()
Returns true if this collection contains no elements.
remove(E e)
Removes a single instance of the specified element from this
collection, if it is present
removeAll(Collection c)
Removes all of this collection’s elements that are also contained
in the specified collection
retainAll(Collection c)
Retains only the elements in this collection that are contained in the specified collection
size()
Returns the number of elements in this collection.
Set
A collection that contains no duplicate elements. There is no order for this collection. In other words, you don’t have to keep the insertion order of the elements.
List
An ordered collection (also known as a sequence). The user of this interface has precise control over where in the list each element is inserted.
Queue
Queues order elements in a FIFO (first-in-first-out) manner. There is no random access with this Collection. Some functions throw exceptions.
add(E e)
Inserts the specified element into this queue
element()
Retrieves, but does not remove, the head of this queue.
offer(E e)
Inserts the specified element into this queue
poll()
Retrieves and removes the head of this queue, or throws if this queue is empty.
HashSet
Implements Set functions
ArrayList
Implements List functions
LinkedList
Implements both List and Queue functions. Your class does not have to have a linked list to implement these.
Iterator
hasNext()
Returns true if the iteration has more elements.
next()
Returns the next element in the iteration and advances the iterator.
remove()
Removes from the underlying collection the last element returned by this iterator
Your Java Collections hierarchy should use only Java arrays in the concrete classes to implement all the methods.
You will test each method of each concrete class with generic parameters of int and string.
