??sa???? st? JAV? (

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??sa???? st? JAV?(µ???? ?)

• ?as???? ?apata???????
• vpap_at_di.uoa.gr
• ????µa ??t??e?µe??st?af?? ?????aµµat?sµ??
• ??d?s???sa ??aµp? ?a????
• ?µ?µa ?????f?????? ?a? ???ep??????????
• ?????? ?a? ?ap?d?st??a?? ?a?ep?st?µ?? ??????

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?as??? S?µe?a

• ??sa??????? ?????f???e? ??a t? ???ssa Java
• ?e???????a Java
• ??µ? e??? Java p?????µµat??
• ?a?a?t???st??? t?? ???ssa? Java
• ?p?p???? ???at?t?te?
• ??af???? µe C

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?st????? St???e?a

• ? Java d?µ?????????e t? 1991 ap? t?? James
  Gosling ?.?. st? Sun Microsystems.
• ??????, ???µ?st??e Oak.
• ??????? st???? ?ta? ? a??pt??? µ?a? ???ssa? p??
  ?a ?ta? a?e???t?t? p?atf??µa?, d??. e????a ?a
  ?pa??e pa?t??.
• ???? t?? a??pt???? t?? ??ad??t???, ? Java ß???e
  p??sf??? ?daf?? ??a a??pt??? efa?µ????.

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?? e??a? ? Java

• ?e t? Java µp??e?? ?a ???e?? ?t? ?a? µe µ?a
  t?p??? d?ad??ast??? ???ssa.
• ?as??eta? st? a?t??e?µe??st?af?? µ??t??? a????s??
  ?a? s?ed?asµ??.
• ??e? p????? ?µ???t?te? st? s??ta?t??? t?? µe t?
  C.

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????te?t????? Java

• ?d?a?te??t?ta
• Compile once, run everywhere

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?etafe?s?µ?t?ta

• ?a a??e?a p??a??? ??d??a Java (.java)
  µeta???tt????ta? se a??e?a bytecode (.class) ?a?
  ??? se ??d??a µ??a??? (machine code).
• ?a bytecode a??e?a e??a? a?e???t?ta µ??a??? ?a?
  µp????? ?a e?te?est??? ap? µ?a Java Virtual
  Machine (JVM).
• ?p?????? JVM s?ed?? ??a ???e p?atf??µa.
• Windows, Linux, Solaris, ?.?.

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??µ? ?????aµµ?t??

• ?? ???se?? ???a?????ta? se .java a??e?a
• Se ???e a??e?? p??pe? ?a ?p???e? t? p??? µ?a
  public ???s?
• S?????? p?a?t??? 1 ???s? a?? a??e??
• ?? ???µa t?? a??e??? ta?t??eta? µe t? ???µa t??
  public ???s?? p?? pe????e?

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Java 2 Platform

• ?p?te?e?ta? ap? 2 µ???
• Java Virtual Machine
• Java APIs
• Java APIs
• ??ß??????e? p?? pa?????? ßas???? s??a?t?se??
  ?t??µe? ??a ???s?
• 3 e?d?se??
• Java 2 Standard Edition (J2SE) desktop ?a?
  d??t?a??? efa?µ????
• Java 2 Enterprise Edition (J2EE) eta??????
  efa?µ????
• Java 2 Micro Edition (J2ME) ???s? se ????t??
  s?s?e???

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Java Virtual Machine

• ??te?e? µeta???tt?sµ??a Java p?????µµata p??
  ???µ????ta? bytecode a??e?a.
• ?a bytecode a??e?a e??a? a?e???t?ta p?atf??µa?
  ?a? µp????? ?a e?te?est??? ap? ?p????d?p?te
  ?p?????st? d?a??te? µ?a JVM.
• ? JVM f??t??e? t?? ???se?? p?? ??e?????ta? ??a ?a
  e?te?este? t? Java p????aµµa (class loader).
• ? JVM ep??????e? (verifies) t?? e?????t?ta t??
  bytecode a??e??? p??? ta e?te??se? (bytecode
  verifier).

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JDK - JRE

• Java Development Kit (JDK)
• ?e??ß????? a??pt???? efa?µ???? st? ???ssa Java
• ?e????e? JVM ?a? Java ß?ß??????e?
• ???a?e?a, ?p?? jar ?a? javadoc
• Java Runtime Environment (JRE)
• ?p?s????? t?? JDK
• ??s?ast??? pe????e? µ?a ???p???s? t?? JVM µe
  s??p? t? d??at?t?ta e?t??es?? p????aµµ?t?? Java.

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???e?a Java

• ???e?a Java
• .java p??a??? ??d??a? (source file)
• .class bytecode a??e?? (pa???eta? ap? compiler)
• .jar s????a s?et???? ???se??
• ?eta???tt????µe ta .java a??e?a p?? pe???????
  ???se??.
• ?? µeta???tt?sµ??? a??e?? .class p?? e?te???µe ?a
  p??pe? ?a pe????e? a???ß?? µ?a main s????t?s?
  (ap? e?e? ?e???? ? e?t??es?)

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F?se?? ??t??es??
java compiler
bytecode file
interpreter (VM)
Source code
Hello.java
Hello.class
javac
java
F?s? ???a?e?? ???d??
WRITE Text editor ???e?? .java
COMPILE Java compiler ???e?? .class (bytecode)
RUN Java interpreter ???d?? p?????µµat??
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Hello World ?

• ??µa 1
• ??µa 2
• javac HelloWorld.java
• ??µa 3
• java HelloWorld

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??p?? ?ed?µ???? st? Java (1/2)

• ???t??e?e?? t?p?? ded?µ???? (primitive data
  types) e?d???? t?p?? ded?µ????, built-ins t??
  ???ssa?, µ??e??? a?e???t?t? p?atf??µa?
• ?e? ???s?µ?p??e?ta? ? ???? new ??a t?
  d?µ??????a µ?a? µetaß??t?? p??t??e???? t?p??
• ?.?. int i 1000

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??p?? ?ed?µ???? st? Java (2/2)

• ??t??e?µe?a
• St? Java ta p??ta (e?t?? t?? primitives) e??a?
  a?t??e?µe?a t?? ???s?? java.lang.Object ?a?
  d?µ????????ta? µe t? ???? new
• ?.?. Date d new Date()
• String s new String(Vassilis)
• ?a?ade??µata
• String a???????a ?a?a?t???? (???s?
  java.lang.String), t?p??? de? ap?te?e? p??t??e??
  t?p? ded?µ????, a??? p?a?t??? µp????µe ?a t??
  s?eft?µaste ?? t?t???
• Arrays, Collections, Vectors, Int, Double,
  MyClass ??p.

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?as??? St???e?a t?? Java

• ?etaß??t??
• ?a??µ??a µe C
• ?e?est??
• ?a??µ??a µe C
• s?????s? Strings
• instanceof operator
• ?.?.
• System.out.println(Size of array
  array.size())

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static - final

• Static
• variable a???e? st?? ???s?
• method ???s?µ?p??e? µ??? pa?aµ?t????
• Final
• variable apa???e?s? a??a??? t?µ?? e?t??
  eµß??e?a?
• method de µp??e? ?a ???e? override
• class de µp??e? ?a ???e? extend

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??µ?? ??????? st? Java

• ?a??µ??a µe C
• ??µ?? ?p??????
• if-else
• switch-case
• ??µ?? ?pa???????
• for
• while
• do while
• break, continue, return, goto

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????se?? import

• ?????? e?t??? st?? compiler ?a ?atast?se? ??at?
  ??a pa??t? (package) st? a??e?? ??d??a.
• ?.?.
• import java.util.Vector //µ??? t?? ???s? Vector
• import java.util. //?,t? pe????eta? st?
  java.util

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??a?e???s? ???µ??

• G??eta? a?t?µata µ?s? e??? ??µat?? t?? garbage
  collector.
• ??a ??µµ?t? µ??µ?? ape?e??e???eta? runtime ?ta?
  p???? de? ?p???e? ???? a?af??? p??? a?t? µ?sa st?
  p????aµµa.
• ? ???st?? de? as???e?ta? (?a? de? µp??e? ?µesa ?a
  t? ???e?) µe t?? ape?e?????s? µ??µ??

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?e?µ????s? ???e?a .jar

• Javadoc
• ??t?µat? pa?a???? te?µ????s?? se µ??f? html
  se??da? µ?s? t?? a??e??? ??d??a Java
• ? ??d??a? s???p???e? µe t? ?e?µe?? te?µ????s??
  ape??e?a? p??sp??as?.
• ???e?a .jar
• ??e??????e? t? d?a?e???s? t?? Java a??e???
• ???p???s? a??e??? se pa??ta

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Java ?a? ??ad??t??

• Java Applets
• Web-efa?µ???? ?a? ??? t?p??? java p?????µµata
• ??p??et???ta? se ?st?se??de?
• ??te????ta? ap? t? JVM e?t?? e??? Web browser
• ?p?st????? sockets, servlets, ?.?.

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???e? ??af???? ap? C (1/3)

• ? Java de? ep?t??pe? p???ap?? ???????µ???t?ta
  (??a ?????? ap??t?ta?)
• ???e ???s? µp??e? ?a ???????µe? t? p??? ap? µ?a
  ???? ???s? (extends)
• Interfaces ??µ?? p?? pe??????? µ? ???p???µ??e?
  s??a?t?se??, ????? µetaß??t??-µ??? ?a? de? e??a?
  ???se??
• ??a ???s? µp??e? ?a ???e? implement pe??ss?te?a
  ap? ??a interface

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???e? ??af???? ap? C (2/3)

• ? Java ?e??e?ta? e? ???e? ap???ste?? ???ssa ap?
  t? C.
• ??e? ?? Java µ???d?? e??a? ?p?? ?? virtual t??
  C.
• ? Java de? ?p?st????e? de??te? (pointers).

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???e? ??af???? ap? C (3/3)

• ? Java de? ?p?st????e? defines, typedefs ?
  preprocessor. ?p?te, de ??e???eta? ??te a??e?a
  ?efa??da? (header files).
• St? Java de? ?p?st??????ta? ?a??????? µetaß??t??.
  ??a??a?t??? static
• St? Java de? ep?t??p??ta? s??a?t?se?? e?t??
  ???se?? (stand-alone functions).

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???te???µe?e? ?????

• The Source for Java Developers,
  http//java.sun.com/
• The Java Tutorials, http//java.sun.com/docs/books
  /tutorial/
• Learning Java, Pat Niemeyer Jonathan Knudsen
• Thinking in Java, Bruce Eckel, http//www.mindview
  .net/Books/TIJ/

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??? ep?µe?? f???

• ???? ?a? ??a???se??
• ?etat??p? ??t??e?µ????
• ??s?d?? / ???d??
• ???a?e?a ???pt????
• ?p?p??s?eta T?µata

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• ???t?se?? ?