Java Reference
In-Depth Information
4.
To allow duplicate elements to be stored in a collection, you need to use a list. A list
not only can store duplicate elements but also allows the user to specify where they are
stored. The user can access elements by an index.
5.
Two types of lists are supported:
ArrayList
and
LinkedList
.
ArrayList
is a
resizable-array implementation of the
List
interface. All the methods in
ArrayList
are defined in
List
.
LinkedList
is a
linked-list
implementation of the
List
interface.
In addition to implementing the
List
interface, this class provides the methods for
retrieving, inserting, and removing elements from both ends of the list.
6.
Comparator
can be used to compare the objects of a class that doesn't implement
Comparable
.
7.
The
Vector
class extends the
AbstractList
class. Starting with Java 2,
Vector
has
been the same as
ArrayList
, except that the methods for accessing and modifying
the vector are synchronized. The
Stack
class extends the
Vector
class and provides
several methods for manipulating the stack.
8.
The
Queue
interface represents a queue. The
PriorityQueue
class implements
Queue
for a
priority queue
.
Q
UIZ
P
ROGRAMMING
E
XERCISES
Sections 20.2-20.7
*20.1
(
Display words in ascending alphabetical order
) Write a program that reads
words from a text file and displays all the words (duplicates allowed) in ascend-
ing alphabetical order. The words must start with a letter. The text file is passed
as a command-line argument.
*20.2
(
Store numbers in a linked list
) Write a program that lets the user enter num-
bers from a graphical user interface and displays them in a text area, as shown in
Figure 20.17a. Use a linked list to store the numbers. Do not store duplicate num-
bers. Add the buttons
Sort
,
Shuffle
, and
Reverse
to sort, shuffle, and reverse the list.
(a)
(b)
F
IGURE
20.17
(a) The numbers are stored in a list and displayed in the text area. (b) The colliding balls are combined.
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