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Document Sample
Programming Java
Java Basics
Incheon Paik
1 Computer Industry Lab.
Java
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
2 Computer Industry Lab.
Java
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
3 Computer Industry Lab.
Java
Byte Code and Java Virtual Machine
Existing Development Environment
Binary
File
Compiler(Pentium) Pentium
Source Binary
Code File
Compiler(PowerPC) PowerPC
Binary
%cc Hello.c –o Hello File
% Hello Compiler(SPARC) SPARC
Run Binary Code
4 Computer Industry Lab.
Java
Bytecodes and the Java Virtual Machine
Java Development Environment
Java
Interpreter
Java Compiler
(Pentium) Pentium
Java Java
Java
Code ByteCode
Interpreter
(Independent on
Java Compiler Platform)
PowerPC
(PowerPC)
Java
%javac Hello.java Interpreter
Hello.class created
% java Hello Java Compiler SPARC
(SPARC)
Run JVM Byte Code
5 Computer Industry Lab.
Java
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
6 Computer Industry Lab.
Java
Classes and Objects
Object
Memory Space to Define State and Operation
Instance of Class
Class
Template of Creating Object
7 Computer Industry Lab.
Java
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 getArea()
Shape Obj = new Ellipse();
Obj.getArea();
Ellipse Rectangle Triangle
Which Area?
getArea()
getArea() getArea()
8 Computer Industry Lab.
Java
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
9 Computer Industry Lab.
Java
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
10 Computer Industry Lab.
Java
Start a Java Application
Java C
Class Name Main Function
“Hello.java” “hello.c”
Main method
class Hello { void main() {
public static void main(String args[]) { printf(“Hello World\n”);
System.out.println(“Hello World”); }
}
% javac Hello.java Compile % cc hello.c –o hello
Run
% java Hello % hello
Result Hello World
11 Computer Industry Lab.
Java
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
12 Computer Industry Lab.
Java
Variables and Assignments
Variable Declaration
type varName; float x, y, x;
Value assignments
varName = value;
int num = 100;
long m = 21234234L
double type : .5 0.8 9e-2 -9.3e-5
float type : 1.5e-3f;
13 Computer Industry Lab.
Java
Strings and Characters
String : sequence of character
String s = “Enter an integer value: ” ;
Char c = „A‟; Unicode
Concatenation Operator „+‟
String s = “Lincoln said: ” + “\” Four score and seven years ago\”” ;
Result :
Lincoln said: “Four score and seven years ago”
14 Computer Industry Lab.
Java
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;
15 Computer Industry Lab.
Java
Type Conversions in Expression
char ch; int i; float f; double outcome;
ch = „0‟; i = 10; f = 10.2f;
outcome = ch * i / f;
int
float
double double
Yes No
double float
Yes No
float long
Yes No
long int
16 Computer Industry Lab.
Java
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
17 Computer Industry Lab.
Java
Comments
Single Line Comment
int i = 10 ; // i is counter
Multiple Line Comment
/*
Some comments
*/
Documentation Comment
/**
Using “javadoc” Tool,
Documentation Comment make document
*/
18 Computer Industry Lab.
Java
Arrays ( One Dimensional)
Definition of One Dimensional Array
type VarName[]
int ia[];
Assign Range to One Dimensional Array
varName = new type[size]
ia = new int[10];
Declaration of One Dimensional Array with Range
type varName[] = new type[size]
int ia[] = new int[10];
19 Computer Industry Lab.
Java
Arrays ( One Dimensional)
Number of elements in Array
varName.length
Initialization of One Dimensional Array
Type varName[] = {e0, … , en};
int j[] = {0, 1, 2, 3, 4, 5};
int k[];
K = j;
Example 1.15
20 Computer Industry Lab.
Java
Arrays ( Multi-Dimensional)
Definition of Two Dimensional Array
type VarName[][];
float fa[][];
Assign Range to Two Dimensional Array
varName = new type[size1][size2];
fa = new float[2][3];
Declaration of Two Dimensional Array with Range
type varName[][] = new type[size1][size2];
float fa[] = new float[2][3];
21 Computer Industry Lab.
Java
Arrays ( Two Dimensional)
Number of elements in Multi-Dimensional Array
varName.length Number of Raw
Number of elements in Each elements of Multi-Dimensional Array
varName[index].length
Initialization of Multi-Dimensional Array
Type varName[][] = {{e00, … , e0n}, {e10,…,e1y}, {e20, …, e2z}};
Example 1.16
22 Computer Industry Lab.
Java
Java Keywords
50 Java Keywords
abstract double int super
boolean else interface switch
break extends long synchronized
byte final native this
case finally new throw
catch float package throws
char for private transient*
class goto* protected try
const* if public void
continue implements return volatile
default import short while
do instanceof static 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.
23 Computer Industry Lab.
Java
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
<applet code="HelloWorldApplet.class" width="150" height="25">
(4) Run Applet using Appletviewer or Applet enabling Web browser
% appletviewer HelloWorld.html
24 Computer Industry Lab.
Java
Exercise
Step 3 (Type Conversion)
Refer to this lecture (slides #16,17)
Step 4 (Array)
Refer to this lecture (slide #22)
25 Computer Industry Lab.
Java
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