Java 소개

1. Java 소개 Java 개요 Sample Programs 객체지향 프로그래밍 개념 환경 설정 및 명령어

2. JRE JVM java 인터프리터 API classes files, ... Source Code Byte Code javac 컴파일러 interpret .class .java 브라우저, or appletviewer Machine Code 생성 / 실행 JIT Compiler Java 개요 • Definition • A general-purpose, high-level, object-oriented programming language developed by Sun Microsystems. (http://java.sun.com) • Originally called OAK ("Green Team") • Java의 특성 • Object-oriented • Platform-independent (Virtual Machine; portability) • Easy; Simplified; (no pointer, automatic garbage collection, single inheritance, ..) • compiled/interpreted, robust, secure, multi-threaded, distributed, ... • Compile/Execution

3. Java 개요 (Cont.) • 자바의 버젼 • Java 1.1.5: announced in 1997, improved user interface, event processing, ... • Java2: beta-testing in 1997; Released in late 1998 (JDK 1.2); Swing, Drag&Drop, improved sound utility, ... • Java2: SDK Standard Edition 1.3 (2000), 1.4 (2002), J2SE 5.0 (tiger), J2SE6.0(mustang), … • http://java.sun.com • 자바 툴 • Kawa, Eclipse, .. • Symantec Visual Cafe, Borland JBuilder, SuperCede, Rogue Wave JFactory, Natural Intelligence Roaster, Metro Works Code Warrior, SunSoft Java Workshop, … • Related Terms • http://webopedia.internet.com/ • applet, AWT, bytecode, CGI, HotJava, interpreter, JAR, JavaBeans, JavaScript, JDBC, JDK, Jini, JIT, JNI, picoJava, Python, RMI, Smalltalk, thin client, virtual machine, JavaOS, JavaRing, JavaCard, EJB, Java Station, …

4. Java 2 Standard Edition • Java 2 Standard Edition includes • Java runtime environment: • A Java virtual machine for the platform you choose • Java class libraries for the platform you choose • Java compiler • Java class library (API) documentation (as a separate download) • Additional utilities, such as utilities for creating Java archive files (JAR files) and for debugging Java technology programs • Examples of Java technology programs

5. Product Life Cycle • Seven Stages • Analysis: investigate a problem and determine its scope and major components • Design: create blueprints (specs) for components that will be developed • Development • Testing: unit tests (individually) and integrated test (together) • Implementation: ship a product, making the product available to customers • Maintenance • End-of-life (EOL)

6. A Sample Program • a Java program • source program • .java • text file format • pico, vi, emacs, ... in Unix; notepad, edit, ... in Windows • javac HelloWorld.java • creates HelloWorld.class • java HelloWorld kawa,eclipse, JBuilder, .... #include <stdio.h> char msg[ ]={‘W’,‘o’,‘r’,‘l’,‘d’}; /* comments here */ main (int argc, char **argv) { printf(“Hello ”); printf(“%s\n”, msg); } class HelloWorld { // 주석 부분 public static void main (String args[]){ String msg = "World"; System.out.print("Hello "); System.out.println(msg); } } 참고: C program

7. Object-oriented Programming • Program • a set of classes and interactions among them • not procedure-oriented • Class • a framework for objects (or instances) of similar characteristics • properties (or, attributes, status variables) • behavior (or, method, function) • retrieve/update the attribute values of instances, execute an action, etc • Class example: Student, Employee, Vehicle, Truck, ... • Example: a monster, called Jabberwock, in a storybook • Making a class for Jabberwork : a simplest form class Jabberwock { } • Attributes • color (orange, yellow, ...), sex (m, f), status (full, hungry), … • Behavior • get angry, cool down, eat a peasant, skip a meal, take a rest, …

8. Jabberwock 예제 • 속성 추가class Jabberwock { String color; // 표준 클래스String sex; boolean hungry; // true 또는 false 값} • Method 추가: 먹이주기void feedJabberwock( ) { if (hungry == true) { System.out.println("Yum -- a peasant!"); hungry = false; } else System.out.println("No, thanks -- already ate."); }

9. Jabberwock 예제 (Cont.) • Method 추가: 속성 보여주기 void showAttributes( ) { System.out.println ("This is a " + sex + " " + color + " jabberwock."); if (hungry == true) System.out.println("The jabberwock is hungry."); else System.out.println("The jabberwock is full."); }

10. Jabberwock 예제 (Cont.) • 클래스 완성 (?) class Jabberwock { String color; String sex; boolean hungry; void feedJabberwock() { if (hungry == true) { System.out.println("Yum -- a peasant!"); hungry = false; } else System.out.println("No, thanks -- already ate."); } void showAttributes() { System.out.println("This is a " + sex + " " + color + " jabberwock."); if (hungry == true) System.out.println("The jabberwock is hungry."); else System.out.println("The jabberwock is full."); }}

11. Jabberwock 예제 (Cont.) • % javac Jabberwock.java% java JabberwockIn class Jabberwock: void main (String argv[ ]) is not defined • 방안 • main( ) 메쏘드에서 Jabberwock 클래스를 이용하도록 한다 • main ( ) 메쏘드를 Jabberwock 클래스에 추가, or • main( ) 메쏘드를 갖는 새로운 클래스를 만든다 public static void main (String arguments[]) { Jabberwock j = new Jabberwock( ); // 새로운 객체 생성 j.color = "orange";j.sex = "male"; j.hungry = true; // 객체 이용 System.out.println("Calling showAttributes ..."); j.showAttributes( ); // 객체 이용 System.out.println("-----"); System.out.println("Feeding the jabberwock ..."); j.feedJabberwock( ); System.out.println("-----"); System.out.println("Calling showAttributes ..."); j.showAttributes( ); System.out.println("-----"); System.out.println("Feeding the jabberwock ..."); j.feedJabberwock( ); }

12. Java Applet • Java Application과 Java Applet • main class • javac Hello.java • appletviewer hello.htm 실행, 또는 웹 브라우저로 hello.html 열기 import java.awt.*; import java.applet.*; Import java.util.*; public class Clock extends Applet { private String greeting[] = { "Hello, world" }; public void paint(Graphics g) { g.drawString(greeting[0], 25, 25); } } <html> <head> <title>Hello</title> </head> <body> <applet code=Hello.class width=250 height=250> </applet> </body> </html> Hello.java Hello.html

13. Java 객체지향 프로그래밍 (Cont.) • 상속성 (Inheritance) • 한 클래스가 다른 클래스로부터 속성과 메쏘드를 물려받는 성질 • superclass; subclass; inheritance hierarchy; • Object 클래스 • method overriding • subclassing • 패키지 (Package) • 관련된 클래스와 인터페이스의 그룹핑 • 인터페이스 (Interface): 추상 메쏘드만 갖는 특별한 형태의 클래스 • java.lang 패키지 : 표준 java 클래스 • 다른 클래스의 참조 • import java.awt.Color 또는 import java.awt.* • import java.applet.*

14. Applet 예제 2: Palindrome • 어떤 문장을 display하는 애플릿 프로그램 작성 • 애플릿 정의 public class Palindrome extends java.applet.Applet {} • 모든 애플릿 클래스는 public 선언 • 폰트 객체 생성 Font f = new java.awt.Font("TimesRoman", Font.BOLD, 36); • 애플릿이 상속 받는 메쏘드 • 애플릿 실행 준비, 마우스 입력 대응, 애플릿 표시, 실행 종료용, ... • paint ( ) 메쏘드의 재정의 (overriding) public void paint(Graphics screen) { // Learn later about Graphics class screen.setFont(f); screen.setColor(Color.red); screen.drawString("Go hang a salami, I'm a lasagna hog.", 5, 40);}

15. Subclassing 예제: Palindrome • a complete program import java.awt.Graphics; import java.awt.Font; import java.awt.Color; import.applet.* public class Palindrome extends Applet { Font f = new Font("TimesRoman", Font.BOLD, 36); public void paint(Graphics screen) { screen.setFont(f); screen.setColor(Color.red); screen.drawString("Go hang a salami, I'm a lasagna hog.", 5, 40); } } • <APPLET CODE="Palindrome.class" WIDTH=600 HEIGHT=100></APPLET>

16. 환경 설정 • JDK 설치 디렉토리 • bin • javac, java, appletviewer, jar, javah, javap, javadoc, ... • demo, jre, include, lib, … • 명령어 경로 지정 (path 변수) • javac, java, appletviewer, ... • Windows 98 예 • autoexec.bat 화일에 set path=%path%; c:\jdk1.4\bin추가 • 실행 sysedit • NT/2000, XP예 • 설정  제어  시스템  고급 탭 에서 path 변수값 변경 • Unix 예 • .cshrc (or .tcshrc) 화일에 set path=($path /usr/local/java/bin) 추가

17. 환경 설정 (Cont.) • 클래스 경로 지정 (CLASSPATH변수) • JDK1.2 이전 버젼의 경우 • set CLASSPATH=.;c:\jdk1.1.7\lib\classes.zip [Windows의 path 설정참조] • setenv JAVA_HOME /usr/local/jdksetenv CLASSPATH .:$JAVA_HOME/lib/classes.zip [Unix] • JDK1.2 이후 버전의 경우 • CLASSPATH 변수를 두지 않거나 또는 . 만 포함해도 됨 • refer to the readme file or installation documents from java.sun.com • explore.kwangwoon.ac.kr 에 홈페이지 만들기 • Refer to http://explore.kwangwoon.ac.kr • public_html directory • explore 서버의 환경은? (JDK 버젼? 명령어 위치? 환경변수 설정? ...)

18. 환경 설정 (Cont.) • Basic Unix commands • ls [-al] [files] ---- list information of files • more filename ---- display the content of a file (긴 화일일때 Space 키, b, q, /, ..) • cd [path] ---- change the current directory (절대/상대 경로) • mkdir dirname ---- create a directory (디렉토리의 삭제 rmdir, 화일삭제 rm ) • chmod [ugo][rwx] file ------ change the permission mode of a file • pico filename • vi [filename] ----- cursor-based screen editor • 이동: h, j, k, l, ^f, ^b, ^u, ^d • 입력/변경: i, a, I, A, c, cw, cc, (입력모드 종료시 ESC 키 필요) • 삭제: x, dw, dd, 5x, 5cw, 5dd (붙여넣기 p 직전명령취소 u 직전명령반복 . ) • 저장/종료: :w, ZZ, :wq!, :q! • man 명령어 ---- on-line 매뉴얼 • logout (또는 exit)

19. javac 컴파일러 • Compiles Java source code into Java bytecodes that can then be used by the java interpreter, Web browsers, and appletviewers. • 용법 javac [options] [source files] [@sourcelist] • .java extension for source file names • Classname.java, if the class is public or is referenced from another source file. • Generates .class file for every class defined in each source file • examples javac MyProgram.java javac -classpath .:/home/avh/classes:/usr/local/java/classes MyProgram.java javac -d /home/avh/classes MyProgram.java (package 위치 지정) • 기타 옵션 -g for debugging (jdb) -encoding … source files encoding name (e.g., KSC5601, SJIS, …) • man javac

20. java 인터프리터 & javap • 용법 java [options] class이름 [argument ...] option: -Dproperty=value • JIT compiler • Sun Microsystems, Asymetrix SuperCede VM, Kaffe bytecode interpreter, Microsoft SDK 2.0 VM, Symantec JIT compiler, ... • 강의노트의 JITintro.htm 문서 참조 • To disable or override the default JIT compiler • setenv JAVA_COMPILER NONE (또는 다른 이름) • % java -Djava.compiler=none class이름 • javap • disassemble the class files • fields, methods, variables, • De-compile of bytecode is possible (source is disclosed)

21. jar • jar - Java archive tool • a Java application that combines multiple files into a single JAR archive file. • also a general-purpose archiving and compression tool, based on ZIP and the ZLIB compression format. • SYNOPSIS jar [ -c ] [ -f ] [ -t ] [ -v ] [ -x file ] [ manifest-file ] destination input-file [ input-files ] • example% jar cvf myJarFile *.class • Manifest file • meta-information about the archive • automatically generated by the jar tool • always the first entry in the jar file • by default, META-INF/MANIFEST.INF • c.f., tar command in Unix • % man jar

22. 기타 명령어 • appletviewer URL_of_HTML • jdb • dbx, gdb like command-line debugger • javah • generates C header and source files that are needed to implement native methods. • javadoc • Java API Documentation Generator • parses the declarations and comments in a set of Java source files and produces a set of HTML pages describing, by default, the public and protected classes, interfaces, constructors, methods, and fields. • javakey • Java security tool which is primarily used to generate digital signatures for archive files. • javaverify

23. Some Tips • Java is case-sensitive • Hello.java.txt when editing in notepad • 여러 클래스로 구성된 화일의 컴파일과 실행 • javac file1.java file2.java ... • java class_file_having_main_function • public class • at most one for each file • the same file name as the class name (except suffix) • naming convention • MyClassName • System.out.println • myFirstMethod

24. 연 습 • Unix 환경과 Windows 환경에서 각각 다음 내용을 실시하라 • 자신의 홈 디렉토리 (또는 '내문서') 아래에 java_work 디렉토리를 생성하고 • Jabberwock와 Palindrome클래스를 작성하여 실행시켜보라. • Hello.java의 화일명을 hello.java로 바꿔서 컴파일하면? 또, Hello.html에 애플릿 태그가 여러 개 있을 때, appletviewer Hello.html의 결과는? • jar 명령을 이용하여 압축저장/내용보기/추출 등을 연습해보라. • javap, javaverify 등의 각 명령어들을 이용해보고, Unix에서 man 명령을 이용하여 on-line 매뉴얼을 살펴보라.

25. 과제 #1 [과제1-2] ‘시계’라고 하는 클래스를 생각해보라. (이름 추가할 것) • 어떤 attribute들이 있겠는가? (3개 이상) 그리고 각 attribute의 가능한 값은 무엇인가? • 어떤 method들이 있겠는가? (3개 이상) • (날짜 출력하는 프로그램, Applet+Application, bollen charged charged=falsed, 출력불가 메시지 출력, 시계 color = ) • Due: 다음 주 – URL 강의게시판에 등록(과제제출 – 애플릿만) • 소스코드와 실행스샷은 첨부로(DOC로 몰아서~!) (9/17까지)