Transcript elc312_day19

Day 19
Chapter
Agenda Day 19
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1st Progress reports OVERdue
Only got one
Quiz 2 on November 10 (next
Class)
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10 problems from chapters 7 & 8
Due Nov 21 (right before
November break)
Capstones Schedule
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1 A, 2 B’s and 1 D
Problem set 4 Posted
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Problem set 3 Corrected
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New Course Grading rubric
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Exams (3 @ 10% each)
30%
Problem Sets (5 @ 8% each)
40%
Group Project
0%
Capstone Project
20%
Pre-professional Conduct (see Contract
on Classroom Behavior)
10%
Today we will discuss
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polygons and polylines
mouse events and keyboard events
Inheritance
Chap 5, 6 & 7
25 M/C 50 mins
We are far behind the anticipated
schedule
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There will be only 5 problems sets
and 3 quiz's
May not get to Chap 12,
Collections
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7-2
Arrays
Chapter
5TH EDITION
Lewis & Loftus
java
Software Solutions
Foundations of Program Design
© 2007 Pearson Addison-Wesley. All rights reserved
7
Outline
Declaring and Using Arrays
Arrays of Objects
Variable Length Parameter Lists
Two-Dimensional Arrays
The ArrayList Class
Polygons and Polylines
Mouse Events and Key Events
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7-4
Polygons and Polylines
• Arrays can be helpful in graphics processing
• For example, they can be used to store a list of
coordinates
• A polygon is a multisided, closed shape
• A polyline is similar to a polygon except that its
endpoints do not meet, and it cannot be filled
• See Rocket.java (page 411)
• See RocketPanel.java (page 412)
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7-5
The Polygon Class
• The Polygon class can also be used to define and
draw a polygon
• It is part of the java.awt pacakage
• Versions of the overloaded drawPolygon and
fillPolygon methods take a single Polygon
object as a parameter instead of arrays of
coordinates
• A Polygon object encapsulates the coordinates of
the polygon
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7-6
Outline
Declaring and Using Arrays
Arrays of Objects
Variable Length Parameter Lists
Two-Dimensional Arrays
The ArrayList Class
Polygons and Polylines
Mouse Events and Key Events
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7-7
Mouse Events
• Events related to the mouse are separated into
mouse events and mouse motion events
• Mouse Events:
mouse pressed
the mouse button is pressed down
mouse released
the mouse button is released
mouse clicked
the mouse button is pressed down
and released without moving the
mouse in between
mouse entered
the mouse pointer is moved onto
(over) a component
mouse exited
the mouse pointer is moved off of a
component
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7-8
Mouse Events
• Mouse Motion Events:
mouse moved
the mouse is moved
mouse dragged
the mouse is moved while the mouse
button is pressed down
• Listeners for mouse events are created using the
MouseListener and MouseMotionListener
interfaces
• A MouseEvent object is passed to the appropriate
method when a mouse event occurs
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7-9
Mouse Events
• For a given program, we may only care about one
or two mouse events
• To satisfy the implementation of a listener
interface, empty methods must be provided for
unused events
• See Dots.java (page 415)
• See DotsPanel.java (page 416)
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7-10
Mouse Events
• Rubberbanding is the visual effect in which a
shape is "stretched" as it is drawn using the
mouse
• The following example continually redraws a line
as the mouse is dragged
• See RubberLines.java (page 419)
• See RubberLinesPanel.java (page 420)
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7-11
Key Events
• A key event is generated when the user types on
the keyboard
key pressed
a key on the keyboard is pressed down
key released
a key on the keyboard is released
key typed
a key on the keyboard is pressed down
and released
• Listeners for key events are created by
implementing the KeyListener interface
• A KeyEvent object is passed to the appropriate
method when a key event occurs
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7-12
Key Events
• The component that generates a key event is the
one that has the current keyboard focus
• Constants in the KeyEvent class can be used to
determine which key was pressed
• The following example "moves" an image of an
arrow as the user types the keyboard arrow keys
• See Direction.java (page 423)
• See DirectionPanel.java (page 424)
• Modified with rubber walls
 DirectionPanelB.java
 DirectionB.java
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7-13
Summary
• Chapter 7 has focused on:
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array declaration and use
bounds checking and capacity
arrays that store object references
variable length parameter lists
multidimensional arrays
the ArrayList class
 polygons and polylines
 mouse events and keyboard events
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7-14
Inheritance
Chapter
5TH EDITION
Lewis & Loftus
java
Software Solutions
Foundations of Program Design
© 2007 Pearson Addison-Wesley. All rights reserved
8
Inheritance
• Inheritance is a fundamental object-oriented
design technique used to create and organize
reusable classes
• Chapter 8 focuses on:
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deriving new classes from existing classes
the protected modifier
creating class hierarchies
abstract classes
indirect visibility of inherited members
designing for inheritance
the GUI component class hierarchy
extending listener adapter classes
the Timer class
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7-16
Outline
Creating Subclasses
Overriding Methods
Class Hierarchies
Inheritance and Visibility
Designing for Inheritance
Inheritance and GUIs
The Timer Class
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7-17
Inheritance
• Inheritance allows a software developer to derive a
new class from an existing one
• The existing class is called the parent class, or
superclass, or base class
• The derived class is called the child class or
subclass
• As the name implies, the child inherits
characteristics of the parent
• That is, the child class inherits the methods and
data defined by the parent class
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7-18
Inheritance
• Inheritance relationships are shown in a UML class
diagram using a solid arrow with an unfilled
triangular arrowhead pointing to the parent class
Vehicle
Car
• Proper inheritance creates an is-a relationship,
meaning the child is a more specific version of the
parent
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7-19
Inheritance
• A programmer can tailor a derived class as needed
by adding new variables or methods, or by
modifying the inherited ones
• Software reuse is a fundamental benefit of
inheritance
• By using existing software components to create
new ones, we capitalize on all the effort that went
into the design, implementation, and testing of the
existing software
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7-20
Deriving Subclasses
• In Java, we use the reserved word extends to
establish an inheritance relationship
class Car extends Vehicle
{
// class contents
}
• See Words.java (page 442)
• See Book.java (page 443)
• See Dictionary.java (page 444)
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7-21
The protected Modifier
• Visibility modifiers affect the way that class
members can be used in a child class
• Variables and methods declared with private
visibility cannot be referenced by name in a child
class
• They can be referenced in the child class if they
are declared with public visibility -- but public
variables violate the principle of encapsulation
• There is a third visibility modifier that helps in
inheritance situations: protected
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7-22
The protected Modifier
• The protected modifier allows a child class to
reference a variable or method directly in the child
class
• It provides more encapsulation than public
visibility, but is not as tightly encapsulated as
private visibility
• A protected variable is visible to any class in the
same package as the parent class
• The details of all Java modifiers are discussed in
Appendix E
• Protected variables and methods can be shown
with a # symbol preceding them in UML diagrams
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7-23
Class Diagram for Words
Book
# pages : int
+ pageMessage() : void
Words
Dictionary
- definitions : int
+ main (args : String[]) : void
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+ definitionMessage() : void
7-24
The super Reference
• Constructors are not inherited, even though they
have public visibility
• Yet we often want to use the parent's constructor
to set up the "parent's part" of the object
• The super reference can be used to refer to the
parent class, and often is used to invoke the
parent's constructor
• See Words2.java (page 447)
• See Book2.java (page 448)
• See Dictionary2.java (page 449)
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7-25
The super Reference
• A child’s constructor is responsible for calling the
parent’s constructor
• The first line of a child’s constructor should use
the super reference to call the parent’s
constructor
• The super reference can also be used to reference
other variables and methods defined in the
parent’s class
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7-26
Multiple Inheritance
• Java supports single inheritance, meaning that a
derived class can have only one parent class
• Multiple inheritance allows a class to be derived
from two or more classes, inheriting the members
of all parents
• Collisions, such as the same variable name in two
parents, have to be resolved
• Java does not support multiple inheritance
• In most cases, the use of interfaces gives us
aspects of multiple inheritance without the
overhead
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7-27