1. Java Computer Industry Lab. 1 Programming Java Java Basics Incheon Paik

2. Java Computer Industry Lab. 2 Contents Contents Background The Java Virtual Machine Applications & Applets Classes & Objects The 3 Principles of Object Oriented Programming Start up Java Variables & Assignments Strings & Characters Arithmetic Operators & Expressions Type Conversion Comments Arrays Keywords

3. Java Computer Industry Lab. 3 Background / History Sun Microsystems Inc. James Gosling 1990, “Green Project” 1991, Develop the Language for Household Products => To General Developing Language Java James Gosling, Arthur Van Hoff, Andy Bechtolsheim Coffee Materials in Indonesia Write once, Run everywhere Spread Rapidly through WWW and Internet

4. Java Computer Industry Lab. 4 Byte Code and Java Virtual Machine Existing Development Environment Source Code Compiler(Pentium) Compiler(PowerPC) Compiler(SPARC) Binary File Pentium PowerPC SPARC Binary File Binary File %cc Hello.c –o Hello % Hello Binary Code Run

5. Java Computer Industry Lab. 5 Bytecodes and the Java Virtual Machine Java Development Environment Java Compiler (Pentium) Java Compiler (PowerPC) Java Compiler (SPARC) Java Interpreter Pentium PowerPC SPARC Java Interpreter Java Interpreter Java Code Java ByteCode (Independent on Platform) %javac Hello.java Hello.class created % java Hello Byte Code Run JVM

6. Java Computer Industry Lab. 6 Java Program Java Application Program Application Program written in general programming language Applet Program running in Web Browser Environment Can be viewed by appletviewer or Web browser with JVM

7. Java Computer Industry Lab. 7 Classes and Objects Object Memory Space to Define State and Operation Instance of Class Class Template of Creating Object

8. Java Computer Industry Lab. 8 The 3 Principles of Object Oriented Programming Encapsulation Control Access the data and method in program code Inheritance Inherit the data and methods of parent class Polymorphism Shape Ellipse Rectangle Triangle getArea() Shape Obj = new Ellipse(); Obj.getArea(); Which Area?

9. Java Computer Industry Lab. 9 The Java Class Libraries java.applet : Applet related java.awt : Abstract Window Toolkit java.awt.event : Event process from awt component java.awt.image : Image processing java.beans : JavaBeans Component java.io : File or Network I/O Support java.lang : Java Language Support java.net : Network related functions java.util : Utility function

10. Java Computer Industry Lab. 10 Java 2 SDK Java 2 Software Development Kit (Java 2 SDK) Java Application or Applet Development and Running Environment Java 2 Runtime Environment (JRE) Java Running Environment Java 2 Standard Edition Java 2 Micro Edition Java 2 Enterprise Edition

11. Java Computer Industry Lab. 11 Start a Java Application “Hello.java” class Hello { public static void main(String args[]) { System.out.println(“Hello World”); } % javac Hello.java % java Hello Compile Run “hello.c” void main() { printf(“Hello World\n”); } % cc hello.c – o hello % hello Hello World Result Java C Class Name Main method Main Function

12. Java Computer Industry Lab. 12 Variables and Assignments Variables Types char 16bits Unicode character data boolean Boolean Variable byte 8 bits signed integer short 16 bits signed integer int 32 bits signed integer long 64 bits signed integer float 32 bits signed floating point number double 64 bits signed floating point number

13. Java Computer Industry Lab. 13 Variables and Assignments int num = 100; long m = 21234234L double type :.5 0.8 9e-2 -9.3e-5 float type : 1.5e-3f; Variable Declaration type varName; Value assignments varName = value; float x, y, x;

14. Java Computer Industry Lab. 14 Strings and Characters String : sequence of character String s = “Enter an integer value: ” ; Char c = ‘A’; Concatenation Operator ‘+’ String s = “Lincoln said: ” + “\” Four score and seven years ago\”” ; Result : Lincoln said: “Four score and seven years ago” Unicode

15. Java Computer Industry Lab. 15 Arithmetic Operators Operators + - * / % += -= *= /= %= ++ -- 5 / 2  2 Why isn’t it 2.5 ? 5 % 2  1 4 / 2  2 4 % 2  0 count * num + 88 / val – 19 % count j += 6;  j = j + 6;

16. Java Computer Industry Lab. 16 Type Conversions in Expression char ch; int i; float f; double outcome; ch = ‘0’; i = 10; f = 10.2f; outcome = ch * i / f; double float int float long int Yes No Yes No YesNo double

17. Java Computer Industry Lab. 17 Type Conversions in Assignment Widening Conversion byte b = 127; int i; i = b; Narrowing Conversion byte b; int i = 258; b = (byte) i; Wrong Conversion byte b; int i = 127; b = i; Right Conversion (But data may be lost) byte b; int i = 127; b = (byte) i; Type Casting

18. Java Computer Industry Lab. 18 Comments Single Line Comment int i = 10 ; // i is counter Multiple Line Comment /* Some comments */ Documentation Comment /** Documentation Comment */ Using “javadoc” Tool, make document

19. Java Computer Industry Lab. 19 Arrays ( One Dimensional) type VarName[] Definition of One Dimensional Array int ia[]; varName = new type[size] Assign Range to One Dimensional Array ia = new int[10]; type varName[] = new type[size] Declaration of One Dimensional Array with Range int ia[] = new int[10];

20. Java Computer Industry Lab. 20 Arrays ( One Dimensional) varName.length Number of elements in Array Type varName[] = {e0, …, en}; Initialization of One Dimensional Array int j[] = {0, 1, 2, 3, 4, 5}; int k[]; K = j; Example 1.15

21. Java Computer Industry Lab. 21 Arrays ( Multi-Dimensional) type VarName[][]; Definition of Two Dimensional Array float fa[][]; varName = new type[size1][size2]; Assign Range to Two Dimensional Array fa = new float[2][3]; type varName[][] = new type[size1][size2]; Declaration of Two Dimensional Array with Range float fa[] = new float[2][3];

22. Java Computer Industry Lab. 22 Arrays ( Two Dimensional) varName.length Number of elements in Multi-Dimensional Array Type varName[][] = {{e00, …, e0n}, {e10, …,e1y}, {e20, …, e2z}}; Initialization of Multi-Dimensional Array Example 1.16 varName[index].length Number of elements in Each elements of Multi-Dimensional Array Number of Raw

23. Java Computer Industry Lab. 23 Java Keywords 50 Java Keywords abstractdoubleintsuper booleanelseinterfaceswitch breakextendslong synchronized bytefinalnativethis casefinallynewthrow catchfloatpackagethrows charforprivatetransient* classgoto*protectedtry const*ifpublicvoid continueimplementsreturnvolatile defaultimportshortwhile doinstanceofstatic strictfp assert (New in 1.5) enum (New in 1.5) The “assert” is recognized as keyword in JDK1.4 compiler, but we could not use it. It can be used it from 1.5.

24. Java Computer Industry Lab. 24 Exercise Step 1 Refer to this lecture (slide #11) Step 2 (How to make & run Applet) (1) Make Applet Program import java.awt.Graphics; public class HelloWorldApplet extends java.applet.Applet { public void paint (Graphics g) { g.drawString(“Hello World!”,5,25); } } // end of Applet (2) Compile(using javac) to create HelloWorldApplet.class (3) Create HTML file (ex; HelloWorld.html) to include applet (4) Run Applet using Appletviewer or Applet enabling Web browser % appletviewer HelloWorld.html

25. Java Computer Industry Lab. 25 Exercise Step 3 (Type Conversion) Refer to this lecture (slides #16,17) Step 4 (Array) Refer to this lecture (slide #22)