Download INTRODUCTION TO OO-PROGRAMMING WITH JAVA

(REALLY SHORT)
INTRODUCTION TO
OO-PROGRAMMING WITH JAVA
Luka Pavlič
University of Maribor
Faculty of Electrical Engineering and Computer Science
Komarno, 16th of Februaryy 2010
OBJECT ORIENTATION
´
Motivation:
«
«
«
«
«
«
´
modularity
loose coupling
strong cohesion
data hiding
separation of interests
REUSE
Approaches
Approaches:
«
«
«
«
encapsulation
inheritance
message passing
polymorphism
COUPLING & COHESION
´
´
´
´
´
Coupling or dependency is the degree to which each
program module relies on each one of the other modules.
Cohesion is a measure of how strongly-related
gy
or focused the
responsibilities of a single module are.
High cohesion often correlates with loose coupling, and vice
versa.
versa
High cohesion and loose coupling are attributes of good
design.
Given two lines of code, A and B, they are coupled when B
must change behavior only because A changed.
changed
They are cohesive when a change to A allows B to change so
that both add new value.
OBJECT ORIENTATION
Is not SE-only topic!
´ In SE it affects all layers of IS: databases,
languages, development environmenst,
production environments,
environments bussiness processes,
processes
standards…
´ Built on success of predecessors
´ Enables component
component-based
based development
´ Today: No.1 paradigm in SE
´
BUT…
BUT
Fool with a tool…
…is still a…
FOOL!
JAVA
Talk is cheap,
show me THE CODE!
Java: language, development and runtime
environment,
i
tools,
l STANDARD!
JAVA - HISTORY
´
1990: Patrick Naughton,
Naughton Bill Joy
Joy, James Gosling
Gosling,
Mike Sheradin
«
How to make development od embeded systems
simple?
´
Java: like C++, OO, strongly typed, inovations
along…
g
´
Java = language + development tools
tools+ runtime
environment + class library
JAVA - HISTORY
´
“Write
Write once,
once run anywhere!
anywhere!”
JJanuary 1996,
1996 JRE was intoduced
i t d
d later
l t
´ Internet wave
´
´
1996:
100 000 web pages with apples
« 200 000 registered domains
«
´
Small apps, console apps, applets
JAVA - HISTORY
´
JDK 1
1.1:
1 1997
«
´
J2SE 1.2:
1 2 1998
«
´
JNDI, JavaSound, HotSpot…
J2SE 1.4:
1 4 2002
«
´
Swing, Java IDL, Collections, strictfp, JIT…
J2SE 1.3:
1 3 2000
«
´
new event model, Java Beans, JDBC, RMI, inner classes…
XML, IPv6, JCA, JSSA, JAAS, WebStart…
Java SE 5.0:
5 0: 2004
«
Language changes
TODAY: JAVA SE 6
´
Web services
Script languages
JDBC Swing
JDBC,
Management
Deployment
Security
PERFORMANCE
Modularity
´
Update 10: Java FX!
´
´
´
´
´
´
´
www jcp org
www.jcp.org
TODAY: JAVA SE 6
LanguageS, libraries, development and runtime
tools, platforms
´ Open Source!
´ Java
J
ME
´ Java SE 6
´ Java EE 5
´
JAVA LANGUAGE PROPERTIES
Simple
´ OO
´ Distributed
´ Iterpreted
´ Robust
´
Secure
S
´ Architecture
c tectu e
independent
´ Transferable
T
f bl
´ High
g p
performace
´ Multithreaded
´ Dynamic
D
i
´
OO & JAVA
Objects + primitives (boolean, int, short, char,
byte, short, float, double)
´ Operation-oriented design
´ Everything
E
thi g within
ithi class…
l
- no hibrids!
hib id !
´ Packages
g
´
TALK IS…
IS
WHERE IS THE CODE?!?
☺☺☺
LEARNING BY DOING IT
Hello
H
ll World,
W ld I can calculate!
l l t !
´ Primitives:
´
byte (8 bits)
« short (16 bits)
« int (32 bits)
« long (64 bits)
« float (32 bits)
« double (64 bits)
« char (16 bits)
« boolean
«
no struct!
´ no typedef!
´ no #define!
´ no pointers!
´
LET
LET’S
S DO IT!
JAVA AS DEVELOPMENT ENVIRONMENT
´
As a development environment, Java
technology provides you with a large suite of
tools:
«A
compiler (javac)
« An interpreter (java)
«A d
documentation
i generator (j
(javadoc)
d )
« A class file packaging tool and so on...
JAVA AS RUNTIME ENVIRONMENT
Java technology applications are typically generalgeneral
purpose programs that run on any machine where
the Java runtime environment (JRE) is installed.
´ There are two main deployment environments:
´
1. The JRE supplied by the Java 2 Software
1
Development Kit (SDK) contains the complete set of
class files for all the Java technology packages, which
includes basic language classes
classes, GUI component
classes, and so on.
« 2. The other main deployment
p y
environment is on yyour
web browser. Most commercial browsers supply a Java
technology interpreter and runtime environment.
«
JAVA AS RUNTIME ENVIRONMENT
´
Java Virtual Machine (JVM)
an imaginary machine that is implemented by
emulating software on a real machine
« provides the hardware platform specifications to which
you compile all Java technology code
«
´
Bytecode
a special machine language that can be understood by
th Java
the
J
Virtual
Vi t l Machine
M hi (JVM)
« independent of any particular computer hardware, so
any computer with a Java interpreter can execute the
compiled Java program, no matter what type of
computer the program was compiled on
«
LET US INTRODUCE MORE CLASSES…
CLASSES
What is class?
´ What is object?
´ What is method?
´ What about attribute?
´ What about memory management?
´
CLASSES…
CLASSES
Car
Natasha’s Car
Type: Mercedes Benz
Model: B
Color: Black
Mike’s Car
Type: Toyota
Model: Yaris
Color: Red
p
printIt()
()
getPrice()
printIt()
getPrice()
…
…
…
…
…
…
…
…
…
…
…
…
…
…
…
…
…
…
…
…
…
…
…
…
…
…
…
…
…
…
…
…
OBJECT-ORIENTED
OBJECT ORIENTED PROGRAMMING=
=
OBJECTS
with
PROPERTIES
and
BEHAVIOUR
And some other “technical” stuff (class vs. object vs. reference, null reference, constructor …)
GARBAGE COLLECTION THREAD
responsible for freeing any memory that can be
freed. This happens automatically during the
lifetime of the Java program.
´ programmer is freed from the burden of having
to deallocate that memory themselves
´
CONTROL STRUCTURES
´
Loops:
« While
« Do-while
« For
«&
´
break, continue, return
Branches:
« If
« Switch
PACKAGES
Similar classes
´ www.komarno.sk
´
´
sk.komarno.myproject
package / import
Where are classes?
´ The purpose of CLASSPATH variable?
´
STANDARD PACKAGES?
Java standard library
´ Java doc availabe online and for download!
´
ENCAPSULATION?
Private?
P
i t ?
´ Public?
´ Package friendly?
´
´
What is static?!?
´
Other modifiers: final, synchronized, abstract,
native, transient
CONSTRUCTORS,
CONSTRUCTORS THIS REFERENCE
There allways is default constructor
´ Defining our own constructor
´ Triggering constructor?
´ this – reference
´ this() - call
´
CLASS STRING
Let us investigate the String
´ toString() method?
´
´
StringBuffer class?
´
How to compare strings? == ?
ARRAYS IN JAVA
arg[] ?!?!
´0
0-based
based indexes
´ Declaration / instantiation difference
´ length attribute
´
´
the notion of null – reference!
PARAMETER PASSING
By reference?
´ By value?
´
GENERALIZATION
´
Main idea:
«
´
´
´
base class,
class superclass
derived class, subclass
single / multiple inheritance
«
´
Abstaction, reuse, similar classes
Be aware: multiple inheritance vs. inheritance depth
Java implementation:
«
«
«
extends
new modifier: protected
reserved word: super
INHERITANCE: NOTE
IS-A relationship!
´1
1-1
1 cardinality!
´
´
Use inheritance correctly!
ABSTRACT CLASS
´
Do we allways want (or CAN!) implement all
methods?
´
Ab t t methods
Abstract
th d and
d classes
l
INTERFACES
We can implement as many interfaces we want!
´ There is multiple inheritance between
interfaces!
´
POLYMORPHISM
The ability of a reference variable to change
behavior according to what object instance it is
holding
´ 3 types:
´
« Inclusion
(overriding)
« Operation (overloading)
« Parametric
BASICS EXTENDED
´
Some benefitial info:
« System.out
y
« java.util.Scanner
« Managing
collections of objects (arrays sux!)
« EXCEPTIONS!