??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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?e??ss?te?a ??µata st? Java

• ???? ?a? ??a???se??
• ?etat??p? ??t??e?µ????
• ??s?d?? / ???d??
• Ge???? S????a
• ???a?e?a ???pt????

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???? ?a? ??a???se??

• ?at? t?? e?t??es? µ?a? µe??d?? µp??e? ?a
  p????????? s?????e? ap??ß?epte?.
• Se a?t?? t?? pe??pt?se?? eµfa?????ta? ????
  (errors) ?a? e?a???se?? (exceptions)
• ? Java ep?t??pe? a?t?µat? ?e???sµ? t?t???? ?a???
  (automated exception handling)
• ??a a?t??e?µe?? t?? ???s?? Error d?µ?????e?ta?
  ???? s?µa?t???? ?a??? p?? de? d??ata? ?a
  a?t?µet?p?st??? sta p?a?s?a e??? p?????µµat??

pa??t? java.lang

• ?.?. NoClassDefFoundError
• (??a pa??de??µa st?? pe??pt?s? p?? ????? ???ste?
  ????? ?at?????? st? µetaß??t? pe??ß?????t??
  CLASSPATH)

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??a???se?? (1/2)

• ??a e?a??es? e??a? ?p???d?p?te ?e?????
  d?ata??sse? t?? ?µa?? e?t??es? e??? p?????µµat??
• ? µ???d?? st?? ?p??a p???a?e?ta? t? sf??µa
  d?µ?????e? ??a exception object, t? ?p???
  pe????e? p????f???e? ??a t? sf??µa p?? p????????e
  ?a? ?a???µaste ?a t? d?a?e???st??µe runtime.
• ?? s?st?µa e????e? t? st??ßa ???s??
• s??a?t?se?? µe s??p? ?a ß?e? ??d??a
• p?? ?a ???e? handle t? exception p??
• p??????e.

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??a???se?? (2/2)

• ? a?a??t?s? ?e???? ap? t? s????t?s? st?? ?p??a
  p????????e t? sf??µa ?a? ?ata???e? st? main (a?
  p??? de? ß?e?e? handler)

• ??a? handler e??a? ?at??????? ?a ???e? handle ??a
  exception a? ? t?p?? t?? exception object
  ta?????e? µe t?? t?p? e?a??es?? p?? ? handler
  µp??e? ?a d?a?e???ste?.
• ?? ß?e?e? ?at??????? handler, t?te e?te?e?ta? ?
  ??d???? t??, d?af??et??? t? p????aµµa
  te?µat??eta?.

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?e???sµ?? ??a???se??

• try catch
• ? ???s? t?? µe??d?? ? e?t??es? t?? ?p??a?
  e?d??eta? ?a p???a??se? µ?a e?a??es? t?p??ete?ta?
  e?t?? t?? µp??? e?t???? try.

try //??d??a? p?? µp??e? ?a //p???a??se?
e?a??es? catch(MyException1 mye1) //
catch(MyException2 mye2) // finally
//

• ?? µp??? catch pe????e? e?t???? p?? ?a
  d?a?e???st??? t?? e?a??es? p?? p????????e.
• finally µp??? e?t???? p?? a??????e? t?? catch
  µp??? ?a? pe????e? ??d??a p?? e?te?e?ta? e?te
  s?µße? e?a??es? e?te ???

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S????e?? ??a???se??

• NullPointerException ???sp??as? a?t??e?µ????
  null
• IllegalArgumentException ????? t?p?? ???sµata
• ArrayIndexOutOfBoundsException ??t?? ?????
  p??a?a
• ArithmeticException ??a??es? µe t? 0
• FileNotFoundException ?? a??e?? de? ß?????e st?
  d?s??

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??e??e?t?µata ?e???sµ?? ??a???se??

• ??a????sµ?? ??d??a ??a a?a?????s? ?a??? ap? t??
  ?a?????? ??d??a
• ??a??t?ta d?a?e???s?? t?? e?a??es?? a????????ta?
  t? st??ßa ???s?? µe??d??
• ???at?t?ta ?e???sµ?? µ?a? e?a??es?? µe
  d?af??et????? t??p???
• ????? catch µp??? µp????? ?a a?af????ta? st? ?d??
  try µp???
• ?????te?a ?? e?d???te?e? e?a???se?? st?? ??d??a
• ???at?t?ta d?µ??????a? ???? ???se?? e?a???se??

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?etat??p? ??t??e?µ????

• ? µetat??p? a?t??e?µ???? (type casting) e??a?
  ???s?µ? ?ta? ?????µe ?a d?a?e???st??µe ??a
  a?t??e?µe?? ?? d?af??et???? t?? e??? t?p??
• ?etat??p?? p??? ta p??? (upcasting)
• ???ta ep?t?ept??
• G????ta? µe ap?? a???es?
• ?etat??p?? p??? ta ??t? (downcasting)
• ?e? e??a? p??ta ep?t?ept??
• G????ta? µe ???s? cast te?est?
• ?p??e? ?a ???e? ?a?????? ? µeta???tt?s? (af?? t?
  cast ?s?? ep?t??peta?), a??? ?a pa?a??e? runtime
  error

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?a??de??µa
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??s?d?? / ???d?? (I/O)

• ? Java ???s?µ?p??e? ???? (streams) ??a ?a
  a?apa?ast?se? p???? e?s?d?? ? p?????sµ??? e??d??
  (p.?. a??e?a st? d?s??, ???a p?????µµata).
• ??? a???????a ap? ded?µ??a (ap?? bytes µ????
  s???eta a?t??e?µe?a).
• ??s?d?? / ???d?? se a??e?a d?s???

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???? ??s?d?? / ???d??

• ???? ??s?d?? (Input Streams)
• ??aß????? ??a teµ???? p????f???a? t? f???
• ???? ???d?? (Output Streams)
• G??f??? ??a teµ???? p????f???a? t? f???

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??p?? ???? (1/2)

• Byte Streams ?/? a??a??et?? t?p?? ded?µ????
• Character Streams I/O ?a?a?t????
• Buffered Streams ???s? d?µ?? buffer ??a
  ap?d?t???te?? a????ep?d?as?
• Scanning and Formatting ??a formatted ?e?µe??

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??p?? ???? (2/2)

• I/O from the command line
• Standard Stream
• Input p???t???????
• Output ?????
• Console
• Data Streams ??a primitive data types ?a? String
  d?ad???? µ??f??
• Object Streams ??a ?p????d?p?te t?p?? a?t??e?µe?a

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Byte Streams

• ???? p?? d?a?e??????ta? ?aµ???? ep?p?d?? ded?µ??a
• S????e?? ???? byte
• FileInputStream/ FileOutputStream
• ???? ?? ?p????p?? t?p?? ???? ßas????ta? st?? ????
  byte.

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?/? ap? a??e?a d?s???

• ?? ???? de? ?p?st??????? ??e? t?? ep???µ?t??
  a????ep?d??se?? µe ta a??e?a p?? ß??s???ta? st?
  d?s??
• File ?e???sµ?? a??e??? a?e?a?t?t?? p?atf??µa?
  ?a? OS
• Random Access File ?p?st????e? µ?-a???????a??
  p??sp??as? sta a??e?a

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?????? ??t??es??

• Ge????, ? ?????? e?t??es?? e??? java p?????µµat??
  a?aµ??eta? µe?a??te??? e??? ?s?d??aµ?? se ??p??a
  ???? ???ssa p????aµµat?sµ?? (??? ?µ?? ?a? ?
  ?????? a??pt???? ?)
• ??t?a ? µeta???tt?sµ???? ??a µ?a µ??a?? ??d??a?
  e??a? e? ???e? ta??te??? ap? t?? ??d??a p??
  e?te?e?ta? ap? ??a? interpreter.
• ?e?t??s? Just-In-Time µeta???tt?s?

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??p??a ?e?e?ta?a S????a

• ??? p??????e ? ???? bytecode
• ?pe?d? ??s?ast??? ap?te?e? µ?a binary
  a?apa??stas? t?? p?????µµat?? p?????sµ??? ?a
  e?te?este? ap? t? JVM (software) ?a? ??? ap? t?
  hardware.
• Se t? ???ssa e??a? ??aµµ??? ? Java
• ?? pe??ss?te??? compilers (p.?. t?? Sun) ??a Java
  e??a? p???? ??aµµ???? se Java, a? ?a? a????? ??
  ß?s? ???s?µ?p??????a? ?? ???sse? C/C.
• Se ?t? af??? t?? JVM a??µa ?a? s?µe?a
  ???s?µ?p????? C (??? ?µ?? ap???e?st???), ??????
  ??a ?????? ap?d?s??. ???µa ?a? JVMs t?? Sun!

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C vs. Java
C JAVA
CoutltltAnswerltltanswer System.out.println("Answer answer)
cingtgtch chSystem.in.read()
void main() public static void main(String args)
int main(int argc,char argv) public static void main(String args)
const int MAX10 final int MAX10
char str String str
int scoresnew int5 int scoresnew int5
delete scores ??? ?????????? ?
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???a?e?a ???pt????

• Eclipse (open source)
• NetBeans (open source)
• JDeveloper (Oracle)
• Visual J (Microsoft)

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???te???µe?e? ?????

• Exceptions, http//java.sun.com/docs/books/tutoria
  l/essential/exceptions/index.html
• Input/Output, http//java.sun.com/docs/books/tutor
  ial/essential/io/
• Type casting, http//www.janeg.ca/scjp/oper/cast.h
  tml

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???t?se?? ?