Aula 01 - Java

Prévia do material em texto

Projeto de Software / P3 
Java sem Orientação a Objetos 
Márcio Ribeiro 
marcio@ic.ufal.br 
twitter.com/marciomribeiro 
You	
  already	
  know	
  
how	
  to	
  program!	
  
3 
Aspects	
  of	
  programming	
  
§  Programming	
  is	
  controlling	
  
§  Programming	
  is	
  teaching	
  
§  Programming	
  is	
  problem	
  solving	
  
§  Programming	
  is	
  crea<ve	
  
§  Programming	
  is	
  abstrac<on	
  
§  Programming	
  is	
  concrete	
  
§  Programming	
  is	
  modelling	
  
But...	
  what	
  is	
  a	
  program?!	
  
5 
What	
  is	
  a	
  program?!	
  
§  Sequences	
  of	
  instruc<ons	
  expressed	
  in	
  specific	
  programming	
  
language	
  
§  Instruc<ons	
  wriFen	
  (programmed/coded)	
  by	
  programmers	
  
§  Model	
  of	
  complex	
  system	
  
Object-­‐Oriented	
  Programming	
  
to	
  model	
  our	
  systems	
  
But	
  first,	
  we	
  need	
  to	
  study	
  
an	
  OO	
  language!	
  
9 
Hello	
  world!	
  
public class HelloWorld {	
	
 public static void main(String[] args) {	
 System.out.println("Hello World!");	
 }	
		
}!
10 
Compiling	
  and	
  Execu<ng	
  
§  javac	
  HelloWorld.java	
  
§  Java	
  Compiler	
  
§  .class	
  file	
  is	
  generated	
  
§  java	
  HelloWorld	
  
§  Java	
  Interpreter	
  
	
  
§  What	
  about	
  the	
  main	
  arguments?	
  
§  java	
  Soma	
  5	
  9	
  
§  args[0]	
  =	
  5	
  
§  args[1]	
  =	
  9	
  
11 
Conven<ons	
  
§  Java	
  is	
  case	
  sensi<ve	
  
§  Why	
  code	
  conven<ons?	
  
§  80%	
   of	
   the	
   life<me	
   cost	
   of	
   a	
   piece	
   of	
   so\ware	
   goes	
   to	
  
maintenance	
  
§  Hardly	
   any	
   so\ware	
   is	
   maintained	
   for	
   its	
   whole	
   life	
   by	
   the	
  
original	
  author	
  
§  Code	
   conven<ons	
   improve	
   the	
   readability	
   of	
   the	
   so\ware,	
  
allowing	
  engineers	
  to	
  understand	
  new	
  code	
  more	
  quickly	
  and	
  
thoroughly	
  
From	
  http://www.oracle.com/technetwork/java/codeconv-­‐138413.html	
  
12 
Java	
  Code	
  Conven<on	
  Examples	
  
public class LinkedList<E> {	
	
 /**	
 * Adds the specified object at the beginning of this list.	
 *	
 * @param object the object to add.	
 */	
 public void addFirst(E object) {	
 addFirstImpl(object);	
 }	
	
 /**	
 * Returns the first element in this list.	
 *	
 * @return the first element.	
 */	
 public E getFirst() {	
 return getFirstImpl();	
 }	
 	
 …	
}!
13 
You	
  can	
  use	
  the	
  javadoc	
  tool…	
  
14 
…	
  to	
  generate	
  HTML-­‐based	
  documenta<on	
  
15 
Java	
  Technology	
  
§  It	
  is	
  a	
  language	
  
§  High	
  level	
  
§  So\ware	
  development	
  process:	
  
	
  
	
  
	
  
§  It	
  is	
  a	
  plaaorm	
  
§  Two	
  components	
  
•  Java	
  Virtual	
  Machine	
  
•  Java	
  Applica3on	
  Programming	
  Interface	
  
16 
Portability	
  
17 
Java	
  Plaaorm	
  
§  Development	
  
§  Compila<on,	
  Execu<on,	
  Debugging,	
  Documenta<on	
  
§  Applica<on	
  Programming	
  Interface	
  (API)	
  
§  Useful	
  classes	
  
§  UI	
  Toolkits	
  
§  Swing,	
  Java	
  2D	
  
§  Deployment	
  
§  Java	
  Web	
  Start	
  
§  Integra<on	
  libraries	
  
§  Databases,	
  Remote	
  Method	
  Invoca<on	
  (RMI)	
  	
  
Eclipse	
  IDE	
  
19 
Eclipse	
  IDE	
  
§  So\ware	
  free	
  
§  Open-­‐source	
  project	
  
§  Developed	
  by	
  Eclipse	
  Founda<on	
  
§  Resources:	
  
§  IBM	
  Ra<onal	
  
§  Borland	
  
§  IDE	
  architecture	
  based	
  on	
  plug-­‐ins	
  
§  JDT	
  (Java	
  Development	
  Tools)	
  is	
  just	
  one	
  plug-­‐in	
  
§  We	
  can	
  implement	
  our	
  own	
  plug-­‐ins	
  
20 
Using	
  Eclipse	
  
§  New	
  project	
  
§  Name	
  
§  Loca<on	
  
§  Layout	
  
§  Perspec<ves	
  
§  Project	
  proper<es	
  
§  Java	
  Build	
  Path	
  
§  New	
  Package	
  
§  New	
  class	
  
§  Running	
  
Let	
  us	
  write	
  a	
  program	
  
in	
  Java	
  using	
  Eclipse!	
  
What	
  can	
  we	
  improve?!	
  
23 
What	
  can	
  we	
  improve?	
  
§  Documenta<on	
  
§  Define	
  and	
  document	
  constants	
  
§  Very	
  important	
  for	
  maintenance	
  tasks	
  
§  BeFer	
  produc<vity	
  
§  Isn’t	
  main	
  big?	
  
24 
Refactoring	
  
	
  
	
  
	
  
	
  
	
  
	
  	
  
§  Examples:	
  
§  Constants:	
  “Replace	
  Magic	
  Number	
  with	
  Symbolic	
  Constant”	
  
§  Method	
  very	
  big:	
  “Extract	
  method”	
  
§  isEmpty	
  boolean	
  example	
  
	
  A	
  change	
  made	
  to	
  the	
  internal	
  structure	
  of	
  
so\ware	
  to	
  make	
  it	
  easier	
  to	
  understand	
  
and	
  cheaper	
  to	
  modify	
  without	
  changing	
  its	
  
observable	
  behavior.