Transcript Programming I

Programming I
Pavel Čech
Faculty of Informatics and Management
University Hradec Kralove
[email protected]
explorer.uhk.cz/pc/www
© Tomáš Kozel, Pavel Čech
© Tomáš Kozel, Pavel Čech
Content
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Introduction into programming
Object oriented modeling
Object oriented programming
Programming in Java
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Objectives
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Introduce students to OOP in Java
Apply apply knowledge acquired in
ALGD
Use advanced tools for application
development
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Resources
McConnell:Rapid Development – Microsoft Press
1996
McConnell:Code Complete – Microsoft Press
1994
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Electronic publications
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The Java Tutorial, Java SDK Documentation www.javasoft.com
Thinking in Java - www.bruceeckel.com, 3.
edition
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Tools
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Java 2 SDK – basic package for
programming in Java
Eclipse – IDE for programming in JAVA
ArgoUML – CASE Tool for object oriented
modeling in UML
These tools can be downloaded from>
http://iris.uhk.cz/kozel/software (uid: student, pwd: prox)
All tools a free
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Terminlogy
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Program = sequence of commands
describing some action
Process = program being executed
(running) program
Processor – device capable of executing a
program
Data – certain kind of objects , that are
appropriately transformed by the program
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Terminology (cont.)
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Source code – programming code written in
a certain programming language
Target code – binary code, that is created
by compilation of source code – is executable
Byte code(Java) – intermediate code that is
create by compilation but it is run by runtime
environment (JRE, JVM)
Library – group of files that contain
subroutines and classes and that can be used
in our program
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Terminology (cont.2)
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Data type – determines type and the size of
value in variables. Indirectly determines the
set of operations that can be applied to the
value.
Variable – “named” block of memory in RAM
for storing values. The size of the memory
block depends on the data type of the value.
Constant – the same as variable but it is not
allowed to changed the value (it is read only).
The constant can be assigned value only once
and that can be only read.
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Programming language
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the means of communication between
computer and the programmer
the means of describing an algorithm
needs to be understandable for both sides
Taxonomy
 Lower level programming lang.
 Higher level …
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Types of prog. lang.
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Structured
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Object oriented
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Separation of data and operations
Older by still commonly used
In many cases faster and efficient
C, Pascal, Basic,…
Modern
Easily maintainable
The code can be re-used
Eiffel, Smalltalk, Java, ...
Hybrid
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Not strictly object oriented i.e. can also be structured (C++,
Object Pascal - Delphi, Visual Basic ...)
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Compiler
=special kind of programs for conversion
of source code into machine code
Types
 Interpreter
 Compiler
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Interpreter
Computer
source
code
input
data
Interpreter
output
data
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Compiler
source code
input data
developer’s
compiler
computer
user’s computer
target code
output data
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The process of compilation
Editor
Library
Debugger
Source
code
Compiler
Linker
(links program)
OBJ code
Target code
relative code
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Running program in Java
Run-time environment
Compilation environment
Class Loader
+
Verifier of
byte code
Source
code (.java)
Java
compiler
Local or
network
transmission
of byte
code
Java
Interpreter
Just-In-Time
compiler
Java
libraries
Java
Virtual
Machine
Runtime system
Byte code
(.class)
OS
HW
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What is object …
Objects
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real world - entities that can be found
everywhere
software – program entities that follow
the rules of real world ones. By
combination of sw. object we create object
oriented programs (systems).
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Real world objects
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Have a name
(object identity)
Have properties
(state)
Do something
(behavior)
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Where can we find objects?
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Thinking about a situation 
We can write some notes with description
and processes in that situation.
Noun can be objects.
Verbs can be operations (behavior) of objects
Objects that are not important when
considering a given problem can be left out
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Object oriented programs(Alan Kay)
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Everything is object. Objects stores data and we can
ask for some services (performing an operation).
Program is a group of objects that comunicates
(send messages = ask for services).
Each object has its own memory space and can
consists of other objects. Complex objects can be
divided into other objects.
Every object belongs to a class.
Every object of the same class has to understand
the same messages and perform the same
operations. Objects can belong into more classes
through inheritance.
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Why use objects in programs?
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It is modern …
They’re closer to
reality
Readable source
code
Advanced tools and
languages
Reusable
Easily maintainable
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What objects can today?
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Behave
Have properties
Inherit from
ancestors
Adapt
Communicate
…
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Terminology revisited
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Object always something particular
with identity called also instance
(Trabant, Audi A6, ...).
Class type of objects, a group in
which a set of objects belong.
Describes general features common
to all objects (instances) in a class
(Car).
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UML
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.... tool ArgoUML
Unified Modeling Language
Graphical language for object modeling
Class
Object
Car
Car
Color
HP
Go()
Brake()
MyFord:Car
attributes
(data)
methods
(operations)
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Software objects
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have name (identity), state, behavior
name is determined by identifier, state
is described by attributes, behaviour is
realized by methods
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Basic OOP principles
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Abstraction
Encapsulation
Inheritance
Polymorphisms
• Communication (messages)
• Association
• Aggregation (composition)
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Abstraction
= separation of important and unimportant
aspects based on a given problem
Example: Calculator from the point of
view of the student
Important aspects:
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Range and precision of numbers
Number and types of operations
Can be kept secret during the test
Unimportant:
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Number of chips on a system board
Type of processor
Exact algorithm of every operation
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Encapsulation
= data and operation forms a atomic whole that
cannot be separated
Data (properties, state) of object and operations
are dependent and influence each other.
Not all features of objects are propagated to
outside (Information hidding)
Data – attribures of an object
Operation – methods of an object
Example: An angry man (state) is more noisy
(behavior) than the calm one.
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Information hiding
Every object can have
„Doughnut“
private elements (attributes, diagram
methods) than cannot be
Public
seen or influence from the
interface
outside of the object
(Information hiding).
Private
These elements are hidden
state
behind so called public
interface .
Example: state and
properties of a man‘s
intestines
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Communication (messaging)
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Objects communicate by sending
messages.
As a consequence of receiving a
message some operation is performed
(message passing = method invocation)
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Association
= represents a general binary relation between
two classes
Each class in association has its role
 For each object with a role we can determine
multiplicity (cardinality) of that relation
Example:
Class Student is in association with the class
Faculty. The student „studies“ and the faculty is
„studied by“.
Multiplicity: Many students (n or *) can study only
one faculty.
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Aggregation
= special kind of association that represents the
relation „part of“
Object can contain other objects. Such objects
are created by aggregating other objects. If
the use of part objects is exclusive in
aggregation we talk about composition.
Example:
Composition: TV x Chip
Aggregation: Student x Lab
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Association in UML
Association
Student
1..*
studuje
1
Faculty
Aggregation
Lab
Student
TV
Chip
Composition
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Inheritance
= ability of objects to inherit attributes
and behavior from ancestors (it is so
called object evolution)
ie. that attributes and behavior can be
further extended and modified
Example:
 Parent -> Children
 Machine -> Vehicle -> Car
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Inheritance in UML
Machine
Vehicle
Car
Truck
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Class attributes
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Attributes are common must be present
for all objects of a particular class
State of object is given by values of
attributes
Sometimes called data, properties
Example: Color, Brand, horse power
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Class methods
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Specify behavior
Sometimes called operation or services
It is custom to hide attributes and use so
called access method to set or retrieve
values
Access methods
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Selectors – reading/retrieving values
Modifiers – setting/writing values
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Information hiding
Rule:
None of the
attributes should
be directly
accessible from the
outside world
->(Black Box)
Method
Method
Attributes
Method
Method
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