ALL ABOUT NETWORKS

• Network
• Interconnection of computers is called network. A network may contain two or
more computers connected with or without a cable.
•  
• The primary purpose of a network is resources sharing, which means a computer
can share its resources, like data, memory, software, hardware, CPU, etc. with
other computers on the network.
• A Network with two computers

Client Server

Client sends request for service

Server sends response to client
• What is the advantage of a network?
• The main advantage of a network is that it makes resource sharing possible among
the connected system, thus helping better utilization of resources.
• Hardware: computer systems, Network Interface Cards (NIC), cables, modems,
hubs, satellites etc…
• Software: Any software, which supports networking features, like Unix, Linux,
Windows NT, etc. so that data can be sent or received.
•  
• Protocol: Protocol could be defined as a Standard procedure for regulating data
transmission between computers. It specifies a way to indentify the destination
and source computers and establish a connection between them to receive or
send data.
•  
• For example: TCP/IP 0r UDP protocols help to divide data into small packets of
several bytes, insert the packets into frames and then send those frames to the
destination computer over the network protocol is the underlying feature of the
software used on the network.
• Which is the most widely used protocol on internet?
• HTTP is the most widely used protocol on internet. The text on the internet is sent
or received from one machine to another using this protocol only.
 Execution of a C program

X1.c X1.obj X1.exe

C Program source code C Program source code Executable code Program output
• Execution of a Java Program

X1.java X1.class JVM

Java Program source code Byte code JVM converts byte code into machine code Program output
• What is the difference between an executable file and a class file?

• Exe file contains machine language instructions for the microprocessor and is
system dependent

• Class file contain byte code instructions for the JVM and is system independent.
• Why Java is suitable for internet?

• Java is suitable for internet because of two main reasons.

• It is system independent and hence its programs can run any type of computer
system available on internet.

• Security.
 INTRODUCTIONS TO JAVA

• History of Java Language

•  
• In 1990, Sun Micro systems Inc (US) Has conceived a project to develop software
for consumer electronics devices that could be controlled by a remote . This
project Stealth Project but later its name was changed to Green Project.
•  
• In January of 1991, Bill Joy, James Gosling, Mike Sheradin, Patric Naughton, and
several others met in Aspen, Colorado to discuss this project.

• Mike sheradin was to focus on Business Development.

• Patrick Naughton was to begin work on Graphics System
• And James Gosling was to identify the proper programming language for the
project.
• Gosling thought C and C++ could be used to develop the project. But the problem
he faced with them is those were system dependent languages and hence could
not be used on various processors. Which the electronic devices might use. So he
started developing a new language. This was completely system independent. This
language was initially called Oak. Since this name was registered by some other
company. Later it was changed to Java.
• Why the name Java?

• James gosling and his team members were consuming a lot of coffee while
developing this language. They felt that they were able to develop a better
language because of the good quality coffee they consumed. So the coffee had its
own role in developing this language and good quality coffee was exported to the
entire world from a place called “Java island”. Hence the fixed the name of the
place for the language as Java. And the symbol for Java Language is coffee cup and
saucer.

• By September of 1994, Nughton and Jonathan Payne started writing WebRunner –

a Java Based web browser, which was later renamed as HotJava. By October 1994,
HotJava was stable and was demonstrated to Sun executives. HotJava was the first
browser, having capabilities of executing applets, which are programs designed to
run dynamically on internet. This time, Java’s potential in the context of the World
Wide Web was recognized.
• Sun formally announced Java and Hot Java at Sun World conference in 1995. Soon
after, Netscape Inc. announced that it would incorporate Java Support in its
browser Netscape Navigator. Later, Microsoft also announced that they would
support Java in their Internet Explorer Web browser, further solidifying Java’s role
in the World Wide Web. On January 23rd 1996, JDK 1.0 version was released. Today
more than 7 million developers use Java and more than 2.75 billion devices run
Java.
 Java Versions, Features and History

• A popular interview question in java is “what is new in Java version X?”. Is that an
intelligent question is debatable. I have summarized below important new features
added in each major java release till now. I target to highlight important features
added in respective release. Apart from below list of features, every release has
enhancements and lots of bug fixes.
 New features in Java 1.8

• Here are the new Java 1.8 features I'll talk about:

• Lambda expressions
• Remove the Permanent Generation
• Small VM
• Parallel Array Sorting
• Bulk Data Operations for Collections
• Define a standard API for Base64 encoding and decoding
• New Date & Time API

• Provide stronger Password-Based-Encryption (PBE) algorithm implementations in

the SunJCE provider
 Features of Java 8

• Here is a brief summary of the enhancements included with the Java 8 release:
Lamda Expression and Virtual Extension Methods Highlighting feature of Java SE 8
is the implementation of Lamda expressions and supporting features to the Java
programming language and platform.

• Date and Time API

• This new API will allow developers to handle date and time in a more natural,
cleaner and easier to understand way.

• Nashhorn JavaScript Engine A new lightweight, high performance implementation

of JavaScript engine is integrated to JDk and is available to Java applications via
existing APIs.

• Improved Security Replacing the existing hand-maintained list of caller sensitive

methods with a mechanism that accurately identifies such methods and allows
their callers to be discovered reliably.
• Java Version SE 7
• Code named Dolphin and released on July 28, 2011.

• New features in Java SE 7

• Strings in switch Statement
• Type Inference for Generic Instance Creation
• Multiple Exception Handling
• Support for Dynamic Languages
• Try with Resources
• Java nio Package
• Binary Literals, underscore in literals
• Diamond Syntax
• Automatic null Handling
• Java Version SE 6
• Code named Mustang and released on December 11, 2006.
• New features in Java SE 6
• Scripting Language Support
• JDBC 4.0 API
• Java Compiler API
• Pluggable Annotations
• Native PKI, Java GSS, Kerberos and LDAP support.
• Integrated Web Services.
• Lot more enhancements.
• J2SE Version 5.0
• Code named Tiger and released on September 30, 2004.
• New features in J2SE 5.0
• Generics
• Enhanced for Loop
• Autoboxing/Unboxing
• Typesafe Enums
• Varargs
• Static Import
• Metadata (Annotations)
• Instrumentation
• J2SE Version 1.4
• Code named Merlin and released on February 6, 2002 (first release under JCP).
• New features in J2SE 1.4
• XML Processing
• Java Print Service
• Logging API
• Java Web Start
• JDBC 3.0 API
• Assertions
• Preferences API
• Chained Exception
• IPv6 Support
• Regular Expressions
• Image I/O API
• J2SE Version 1.3
• Code named Kestrel and released on May 8, 2000.
• New features in J2SE 1.3
• Java Sound
• Jar Indexing
• A huge list of enhancements in almost all the java area.
• J2SE Version 1.2
• Code named Playground and released on December 8, 1998.
• New features in J2SE 1.2
•  
• Collections framework.
• Java String memory map for constants.
• Just In Time (JIT) compiler.
• Jar Signer for signing Java ARchive (JAR) files.
• Policy Tool for granting access to system resources.
• Java Foundation Classes (JFC) which consists of Swing 1.0, Drag and Drop, and Java
2D class libraries.
• Java Plug-in
• Scrollable result sets, BLOB, CLOB, batch update, user-defined types in JDBC.
• Audio support in Applets.
• JDK Version 1.1
• Released on February 19, 1997
• New features in JDK 1.1
• JDBC (Java Database Connectivity)
• Inner Classes
• Java Beans
• RMI (Remote Method Invocation)
• Reflection (introspection only)
•  
• JDK Version 1.0
• Codenamed Oak and released on January 23, 1996.
 Characteristic of java

• Simple , small and familiar

• Object oriented
• Distributed
• Robustness
• Secure
• Architecture Natural or Platform Independent
• Portable compiled & Interpreted
• High Performance
• Multithreaded & Interactive
• Dynamic and extensible
 Simple small and Familiar

• Syntax is just like C++

• It is very easy to learn
• It does not use any header files
• It eliminates operator overloading and virtual base classes
• It is small language so we can writes s/w that can run small computer
 Object Oriented

•  
• It’s purely object oriented language
• Everything in java is an object
• All programs data reside inside the objects and classes
• Distributed
•  
• It has strong network facilities. So we can create and application network
• Use java we can open and use the application on internet. This facility helps the
users from different place to work together on a single application
• Robustness
•  
• In many languages attention is not given an memory management and exception
concept. But in java we are use the advanced techniques called garbage collections
and exception handling
•  
• Secure
• Java is a programming language on internet so security becomes an important
issue. Before a java code from internet is interpreted, and security check is applied
on internet.
•  
• Digitally signing
•  
• Java has a facility to sign our java code before send it.
• At the receiving and the receiver can tally the signature if the signature is matches,
the codes reached correctly this concepts is called digitally signing.
•  
 • Architecture Natural Language
Source code

Java compiler

Byte code
011011011
100110010

Java compiler generates platform independent code from the source code. It cable to
run any type of system that is called byte code (class file)
• Portable
• In java size of primitive data types or machine independent so java is portable
language

• High Performance 
• Since java interpreter uses by the codes so the performance is high
•  
• Multi threaded and Interactive
• Multi threaded means handling more than one jobs at a time
• Java also supports by interactive programs

• Dynamic and Extensible

• It capable to create the passes and executes the method at the runtime so it’s
dynamic. We can extern the feature of java language so it is extensible.
• Parts of Java 
• Sun Micro System Inc has divided Java into 3 parts Java SE, Java EE, Java ME. Let us
discuss them in brief here:
•  
• Java SE: It is the Java Standard Edition and it contains basic core java classes. This
edition is used to develop standard applets and application.
•  
• Java EE: It is the Java Enterprise Edition and it contains classes that are beyond
Java SE. In fact, we need Java SE in order to use many of the classes in Java EE
mainly concentrates on providing business on a network.
•  
• Java ME: It stands for Java Micro Edition. Java ME is for developers who develop
code for portable devices, such as a PDA or a cellular phone. Code on these
devices needs to be small in size and should take less memory.
 Differentiate JVM JRE JDK JIT : Getting Started

• Java Virtual Machine (JVM) is an abstract computing machine. Java Runtime

Environment (JRE) is an implementation of the JVM. Java Development Kit (JDK)
contains JRE along with various development tools like Java libraries, Java source
compilers, Java debuggers, bundling and deployment tools.
 JDK (Java Development Kit):

• Java Developer Kit contains tools needed to develop the Java programs, and JRE to
run the programs. The tools include compiler (javac.exe), Java application launcher
(java.exe), Appletviewer, etc…

Compiler converts java code into byte code. Java application launcher opens a JRE,
loads the class, and invokes its main method.

JDK (Java Development Kit) is a software development kit to develop applications

in Java. When you download JDK, JRE is also downloaded, and don't need to
download it separately. In addition to JRE, JDK also contains number of
development tools (compilers, JavaDoc, Java Debugger etc).
 JRE (Java Runtime Environment):

• JRE = JVM + Java Packages Classes(like util, math, lang, awt,swing etc)+runtime
libraries.

• Java Runtime Environment contains JVM, class libraries, and other supporting files.
It does not contain any development tools such as compiler, debugger, etc.
Actually JVM runs the program, and it uses the class libraries, and other supporting
files provided in JRE. If you want to run any java program, you need to have JRE
installed in the system.

• JRE (Java Realtime Environment) is a software package that provides Java class
libraries, along with Java Virtual Machine (JVM), and other components to run
applications written in Java programming. JRE is the superset of JVM.
 JVM (Java Virtual Machine):

• When we compile a Java file, output is not an .exe but it’s a .class file. This .class is
known as Java byte code, It has the Java byte codes which can be understood by
JVM.

• Java Virtual Machine interprets the byte code into the machine code and execute
it. It is responsible for all the things like garbage collection, array bounds checking,
etc… JVM is a cornerstone of the write-once run-anywhere value of Java
programs.

• Note: JVM is platform dependent but it makes the Java platform independent.

• The Java Virtual Machine provides a platform-independent way of executing code;

programmers can concentrate on writing software, without having to be
concerned with how or where it will run.
 JIT (Just-in-time Compiler):

• JIT also known as dynamic translation. JIT is the part of the Java Virtual Machine
(JVM) that helps to speed up the execution time. Parts of the byte code that have
similar functionality at the same time complied by JIT and saves time needed for
compilation. It translates the instruction set of a Java virtual machine (JVM) to the
instruction set of a specific CPU.