Java Network Programming-Computer Networks-Lecture, Lecture notes of Computer Networks

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Java Network Programming

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About this course

• Duration:

o 2 weeks o 5 days a week o Two lecture and two labs daily

• Course material

o Books o Lectures

• Course completion exam
• Course Completion Certificates

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JAVA

o Java is a simple, secure object oriented language, it inherits features from C/C++. o Developed by James Gosling, Patrick Naughton, Chris Warth, Ed Frank, Mike Sheridan at Sun Microsystems in 1991 o Initially named “Oak” o Primary motives

• Platform independence
• Embedded Software for electronic devices e.g. remote control.
• C/C++ could solve the problem but require separate compiler for each platform o Failed to gain the primary objectives and turned towards the internet programming, later it gain success as internet programming language.

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Highlighted Features of Java

• Platform Independent o Once compiled can be deployed on any platform without recompilation
• Platform independence is achieved by
  • Java Bytecode
    • Highly optimized set of instruction designed to be executed by JVM
    • Java programs are initially compiled to bytecode.
    • Bytecode is remains same for all platforms
  • Java Virtual Machine
    • A java virtual machine converts byte code to native machine code.
    • Different platform require different implementation of JVM
    • All JVM have same standard for bytecode
• Internationalization

o The unicode character set

• Pluggable look and feel
• Interpreted Language
  • Less efficient than languages that generate native code about 1/2 to 1/ times

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Application Development tools

• Java Development Kit o Non-IDE command like resource kit contains core java library o JDK is part of all java development environment o Developed by Sun
• Borland Jbuilder o A rapid application development tool , by Borland ( Inprise)
• Net Beans
• Eclipse
• Visual Age o A rapid application development tool by IBM
• Visual Café o An integrated development tool by Symantec Corporation
• Visual J++ o By Microsoft Corporation
• Others e.g. Kawa

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Java Development Kit~JDK

• Developed by Sun-microsystem
• Provides

o Core development tools o Standard set of libraries

• Standard tools includes

o Javac

• Java compiler o Java
• Java interpreter o Javah o javap o Javadoc o others

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Flavors of Java Programs

• Java Programs fall in the following major categories
• Applets
  • For web browsers
  • Examples web animations, online chat clients, online purchase clients etc.
• Applications
  • Standalone or client server
  • Examples: database program, a face recognition program
    • Text/Command Line applications
    • GUI base applications
• Server side programs
  • JSP
  • Servlets
• Embedded Applications
  • Designed to be executed in embedded devices such as electronic devices
  • microwave oven scheduler

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How

Java

Works

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A simple Java Program

public class HelloWorld {

public static void main ( String s[] ) {

System.out.println(“Hellow World”);

The program should be saved to a file named HelloWorld.java

main method

Class Name

a Class

an object method

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Compiling and Executing HelloWorld Program

Open jdk/bin on command prompt and write

javac HelloWorld.java It will generate the HelloWorld.class on command prompt write java HelloWorld Output Hello World c:> cd jbuilder C:>jbuilder7>cd jdk1.3. C:>jbuilder7>jdk1.3.1> cd bin C:>jbuilder7>jdk1.3.1> bin>javac HellowWordl.java C:>jbuilder7>jdk1.3.1> bin>java HelloWordl Hello World C:>jbuilder7>jdk1.3.1> bin>

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Primitive Data Types

Numeric Data Types

byte 8 bits

short 16 bits

int 32 bits

long 64 bits

float 32 bits

double 64 bits

Non-Numeric

char 16 bit (java uses unicode character set,that is the unification of many character set of other languages and can represent almost each human language character set , a major part of this set is empty)

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Declaring and initializing variables

Identifiers

An identifier must start with a letter, an underscore, or a dollar sign.

• An identifier cannot contain operators, such as +, -, and so on.
• An identifier cannot be a reserved word.
• An identifier cannot be true, false, or null.

Declaring and Initializing Integers and Floats

int i = 34;

long l = 1000000;

float f = 100.2f; or float f = 100.2F;

double d = 100.2d or double d = 100.2D;

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Declaring and initializing cont..

Constants final data_type CONSTANTNAME = VALUE;

• final double PI = 3.14159;
• final int SIZE = 3;

Strings

• String are not primitive data types
• Implemented by a class called String
• Can be used like primitive data type
• Example String country=“Pakistan”;

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Displaying values

System.out.println(“Any string”+variable+”Other string”);

Exanmple

public class Student{

public static void main(String s[]){ int code=911; System.out.println(“Mr. Anonymous “+code); System.out.print(“Mr. “); System.out.print(“ Anonymous “); System.out.print(code); }

}

Mr.Anonymous 911

Mr.Anonymous 911