introduction à la programmaion java.pdf

7/30/2019 introduction la programmaion java.pdf

1/48

Programmation 2Introduction la programmation Java


2/48

Course information

Lectures: 6 x 2 hours

TPs: 6 x 2 hours Lecturer: Alexandru Costan

alexandru.costan at inria.fr

TP instructor: Delphine Demangedelphine.demange at irisa.fr
mailto:[email protected]:[email protected]:[email protected]


3/48

Contents

Introduction to Java programming language

Inheritance and applications Introduction to Swing

Swing interactions

Threads Perspectives


4/48

Readings Main references (Sun)

The Java Language Specification The Java Virtual Machine Specification The Java Tutorial Books

Java Series Books (on the Sun website)

Further readings Le langage Java: Concepts et pratique -le JDK 5.0, Irne Charon Introduction la programmation objet en Java: Cours et exercices, Jean Brondeau Algorithmique et programmation en Java: Cours et exercices corrigs, Vincent Granet Java 2.0: De l'esprit la mthode, Michel Bonjour, Gilles Falquet, Jacques Guyot, Andr

Le Grand

Algorithms in Java: Fundamentals, Data Structures, Sorting, Searching, and GraphAlgorithms,Robert Sedgewick

Course website http://www.irisa.fr/celtique/demange/ens/prog2/
http://www.amazon.fr/Algorithms-Java-Fundamentals-Structures-Searching/dp/0201775786/http://www.irisa.fr/celtique/demange/ens/prog2/http://www.amazon.fr/Algorithms-Java-Fundamentals-Structures-Searching/dp/0201775786/http://www.amazon.fr/Algorithms-Java-Fundamentals-Structures-Searching/dp/0201775786/http://www.amazon.fr/Algorithmique-programmation-Java-exercices-corrig%C3%A9s/dp/210048463Xhttp://www.amazon.fr/Introduction-programmation-objet-Java-exercices/dp/2100041061http://www.amazon.fr/langage-Java-Concepts-pratique/dp/2746212129http://java.sun.com/docs/books/javatutorial/tutorial-all.htmlhttp://java.sun.com/docs/books/jvms/http://java.sun.com/docs/books/jls/http://www.irisa.fr/celtique/demange/ens/prog2/http://www.irisa.fr/celtique/demange/ens/prog2/http://www.amazon.fr/Algorithms-Java-Fundamentals-Structures-Searching/dp/0201775786/http://www.amazon.fr/Algorithms-Java-Fundamentals-Structures-Searching/dp/0201775786/http://www.amazon.fr/Algorithms-Java-Fundamentals-Structures-Searching/dp/0201775786/http://www.amazon.fr/Algorithms-Java-Fundamentals-Structures-Searching/dp/0201775786/http://www.amazon.fr/Java-2-0-Distribution-dapplications-Internet/dp/2711786471/http://www.amazon.fr/Java-2-0-Distribution-dapplications-Internet/dp/2711786471/http://www.amazon.fr/Algorithmique-programmation-Java-exercices-corrig%C3%A9s/dp/210048463Xhttp://www.amazon.fr/Algorithmique-programmation-Java-exercices-corrig%C3%A9s/dp/210048463Xhttp://www.amazon.fr/Introduction-programmation-objet-Java-exercices/dp/2100041061http://www.amazon.fr/Introduction-programmation-objet-Java-exercices/dp/2100041061http://www.amazon.fr/langage-Java-Concepts-pratique/dp/2746212129http://www.amazon.fr/langage-Java-Concepts-pratique/dp/2746212129http://www.sun.com/books/java_series.htmlhttp://www.sun.com/books/java_series.htmlhttp://java.sun.com/docs/books/javatutorial/tutorial-all.htmlhttp://java.sun.com/docs/books/javatutorial/tutorial-all.htmlhttp://java.sun.com/docs/books/jvms/http://java.sun.com/docs/books/jvms/http://java.sun.com/docs/books/jls/http://java.sun.com/docs/books/jls/


5/48

Evaluation

Small project: 20% Main project: 50%

Written exam: 30%


6/48

Introduction to Javaprogramming language


7/48

History

1991: developed by Sun Microsystems as a smallprogramming language for embedded householddevices

Initially called Oak

1995: Java 1.0 released Write Once, Run Anywhere

Became popular with webpages running applets

1997: Standard SDK

JRE


8/48

History

1998: Java 1.2, multiple types of platforms J2EE J2ME

J2SE 2004: Java 5

Collections, enumerate concurrent programming

2006: open source, GPL

Sun: "Java's evangelist"

Nowadays, widely accepted as a multi-purpose programminglanguage / technology

Portable, safe

Object-oriented, component-oriented


9/48

Why Java?

Easy to use Addresses the weaknesses of older programming languages

Object-oriented

Supports good programming styles

Portability - Interpreter environment Safe

Data always initialized, references always type-safe Access to "private" or "package private" data and methods is

rigidly controlled.

Features

Built-in multi-threading


10/48

Compiling and interpreting

Program source code compiled into bytecode Bytecode is executed in an interpreter environment

(Virtual Machine)

Java

program.java Compiler

Javabytecode

program.class

Java VM forWindows

Java VM for

Linux

Java VM forMac OS


11/48

Types of Java applications

Desktop application - J2SE Java Application: normal Java application running on

desktops; console or GUI

Java Applet: embedded application running within Webbrowsers

Server application - J2EE

JSP, Servlets Mobile (embedded) application J2ME Java Card

Java RMI - distributed programming


12/48

Types of Java applications

Desktop application - J2SE Java Application: normal Java application running on

desktops; console or GUI

Java Applet: embedded application running within Webbrowsers

Server application - J2EE

JSP, Servlets Mobile (embedded) application J2ME Java Card

Java RMI - distributed programming


13/48

Object Oriented Programming

Procedural programmingvs. OOP

Limitations of proceduralprogramming:

Data are separated from processes

Passive data, active processes No guarantee of data consistancy

and constrainsts

Difficulty in code maintenance


14/48

Object Oriented Programming

Addresses these limitations Data come together with

related processing code

Guarantee of data consistency Easier maintenance Define things(objects) which

can either do something or havesomething done to them

Create a type(class) for theseobjects so that you dont have toredo all the work in defining an

objects properties and behavior


15/48

Hello World

Compile:javac TestGreeting.java Run:java TestGreeting

Result: Hello, world


16/48

Classes

Are the templates to create objects (byinstantiation)

Each object has the same structure andbehavior as the class from which it was

created


17/48

Declaring a class

public classCLASSNAME {

}


18/48

Declaring a class

public classCLASSNAME {

}

fields

methods


19/48

Classes

Definition

Instance


20/48

Constructors

Every class has a special method(s) called constructor toinitialise objects data members

A constructor is invoked when an object is to be created/allocated by using the newoperator

Baby myBaby1 = new Baby();

A class may have multiple constructors (overloading) Distinguished at compile time by having different parameter lists

Baby myBaby2 = new Baby("Madonna", false);

Baby myBaby3 = new Baby("Bono", 2.5);

When no constructors are defined in source code, adefault constructor that requires no arguments and doesnothingwill be automatically provided.


21/48

Constructorspublic class Baby{

String name;

boolean isMale;

double weight;

public Baby(){

name = "John Doe";isMale = true;

weight = 3.1;

}

public Baby(String babyName, boolean gender){

name = babyName;

isMale = gender;

weight = 3.1;}

public Baby(String babyName, double kilos){

name = babyName;

isMale = true;

weight = kilos;

}

}


22/48

Access modifiers

public:Accessible anywhere by anyone

protected:Accessible only to the classitself and to its subclasses or other classes inthe same package

private: Only accessible within thecurrent class

default (no keyword): accessible within thecurrent package


23/48

Data types

Java is a strongly typed language Every variable must have a declared type

There are two kinds of data types

Primitive data types Variables are manipulated via variable names int a = 5;

Reference types Arrays and objects Manipulated via references GradeBook myGradeBook = new GradeBook();


24/48

Primitive data types


25/48

Assignment operator =

Copy the reference's content, NOT thereferred object

Baby tom = new Baby("Tom", 2);

Baby alex = new Baby("Alex", 3);

tom = alex

alex.weight = 5;

System.out.print(tom.weight);// 5


26/48

Assignment operator =

Copy the reference's content, NOT thereferred object

Baby tom = new Baby("Tom", 2);

Baby alex = new Baby("Alex", 3);

tom = alex

alex.weight = 5;

System.out.print(tom.weight);// 5


27/48

Reference types

Objects are manipulated via references Object references store object locations in computers memory NO explicit pointers in Java (no direct access to the references) NO pointer operators

Directly handle attributes and methods

Assignments (=) of references do NOT copy objects content

public class Baby{

String name;

boolean isMale;

double weight;

public Baby(){

name = "John Doe";

isMale = true;

weight = 3.5;

}public void eat(double food){

weight = weight + food;

}

Baby tom;

tom = new Baby();

tom.eat(2.1);

Baby tom name

isMale

weight

a Baby object

Heap memory


28/48

Equality operators: ==and !=

Compare the content of the variables Value of primitive data

Value of references i.e. check if they point to the same object, NOT whether the contentof the objects are the same

int n1 = 1;

int n2 = 1;

System.out.println(n1 == n2); //true

Baby baby1 = new Baby("Tom");


System.out.println(baby1 == baby2); //false


29/48




int n1 = 1;

int n2 = 1;






30/48




int n1 = 1;

int n2 = 1;






31/48

Garbage collection

To reclaim the memory occupied by objects that are nolonger in use

Programmers dont have to deallocate objects Java Virtual Machine (JVM) performs automatic garbage

collection

Method finalize() is called by JVM, not by programmers Guarantees no memory leaks

However, theres no guarantee when/whether an object isfreed before the program terminates

Might not be needed as memory is still available Clean-up tasks must be done explicitly by other clean-up methods


32/48

The this reference

this: the reference that points to the current object(from inside).

usage ofthis: explicit reference to objects attributes and methods

parameter passing and return value

calling constructor from inside constructor


33/48

The this reference

this: the reference that points to the current object(from inside).

usage ofthis: explicit reference to objects attributes and methods

parameter passing and return value

calling constructor from inside constructor


34/48

Static types and methods

Applies to fields and methods Means the field/method

is defined for the class declaration is not unique for each instance

Static methods can't access non-static attributes can't call non-static methods


35/48

Packages

Each class belongs to a package Classes in the same package serve a similar

purpose Packages are just directories Classes in other packages need to be imported

All classes "see" classes in the same package(no import needed) All classes "see" classes in java.lang

ex:java.lang.String; java.lang.System


36/48

Packages Definition

package path.to.package.foo;

class Foo{

...}

Usageimport path.to.package.foo.Foo;

import path.to.package.foo.*;

Specific packagesjava.lang, java.util, java.io, java.awt,

java.net, java.applet


37/48

Standard I/O

Three stream objects automatically created when aJava program begins executing

System.out: standard output stream object

normally enables a program to output data to the screen(console)

ex:System.out.println("some text");

System.err: standard error stream object

normally enables a program to output error messages to thescreen

System.in: standard input stream object normally enables a program to input bytes from the keyboard


38/48

Arrays

Indexed list of values: TYPE[] The index starts at 0 and ends at length-1.int[] values;

values = new int[5];

int size = values.length;

int[][] M = new int[3][2];

int[] primes = {1,2,3,5,7};


39/48

Strings

String - constant strings (non-modifiable)String ch1 = new String("bonjour");

String ch2 = "au revoir";String ch3 = ch1+ch2;

int i = ch1.indexOf('j');

char c = ch2.charAt(3);

StringBuffer - mutable stringsStringBuffer sb1 = new StringBuffer(ch1);

sb1.append('x');

sb1.insert(3,"yyy");


40/48

Constant data

final attribute primitive data types: constant values

reference types: constant referencesfinal int number = 7;

number = ...; //NO!

number++; //NO!

final Robot R2D2 = new Robot();

R2D2 = ...; //NO!

R2D2.positionX = 15; //YES!

R2D2.positionY = 20; //YES!


41/48

Constant data



number = ...; //NO!

number++; //NO!


R2D2 = ...; //NO!




42/48

Constant data



number = ...; //NO!

number++; //NO!


R2D2 = ...; //NO!




43/48

Constant data



number = ...; //NO!

number++; //NO!


R2D2 = ...; //NO!




44/48

Constant data



number = ...; //NO!

number++; //NO!

final Robot R2D2 = new Robot();R2D2 = ...; //NO!




45/48

Constant data



number = ...; //NO!

number++; //NO!

final Robot R2D2 = new Robot();R2D2 = ...; //NO!




46/48

Exception handlingIf a method p() uses a method q() susceptible to trigger an exception:

catch and handle the exception

void p(){ ...

try { ... q() ...}

catch(xxxException e){//handling e}}

or, propagate the exception

void p() throws xxxException{ ... q() ...}

xxxException:derived from Exception or RuntimeExceptionex: IOException, NullPointerException,

NumberFormatException, IndexOutOfBoundsException

finally{ ... } associated with a try{...} block, typically forcleanup purposes (closing files, freeing resources)


47/48

Create your own exceptions By extending the java.lang.Exception class Typically define constructor(s) and redefine the toString()

method

public class ExceptionRien extends Exception { int nbChaines; public ExceptionRien(int nombre) {

nbChaines = nombre;

}

publicString toString() {

return "ExceptionRien : aucune des " + nbChaines + "

chaines n'est valide";}

}

Usage:... throw new ExceptionRien();


48/48

To take away

object oriented programming language

data centric classes: models; objects: instances

objects handled through references

extensive API

Documents

introduction à la programmaion java.pdf