Introduction To Java Programming language
Software is a development process which converts the imaginaries into reality by writing
comes set of programs.
In IT we
develop two types of applications. They are stand alone applications and
distributed applications.
A stand alone application is one which runs in the
context of local disk. All stand alone applications are not sharable. S ystem
software and application software come s under stand alone applications.
In IT we develop two types of applications. They are stand alone applications and distributed
applications.
A stand alone application is one which runs in the context of local disk. All stand alone applications are not sharable. System software and application software comes under stand alone applications.
System software is used for developing functionality of hardware devices. Examples are C and ALP (Assembly Language Programming).
Application software is used for developing organizations oriented applications. This is also known as backend software’s. Examples are dbase, dbase III plus, FoxPro, oracle versions released till now.
Internet software is used for developing distributed applications.
A distributed application is one which can be accessed
across the globe. Distributed application is also one which runs in the con
test of the World Wide Web. To develop distributed applications we must use
client-server architecture.
In client-server
architecture we must hare at least two programs they are client program and
server program. A client progra m is one which always makes a request to get
the service from the server. A server program is on e which will do three
operations receiving the request from client, processing the client request and
sending the response to the client.
All the above three
operati ons are performed by the server concurrently. In order to exchange the
data between client and server we must use a protocol called http (hypertex t
transfer protocol).
Protocol
is a set of values which are defined to exchange the data betwe en client and
server either locally or remotely.
In order
to develop distrib uted applications, two software companies c ame forward
whose names are Microsoft System and Sun Micro System.
Microsoft System has developed a technology called DOT NET and Su n Micro System has developed a technology called JAVA. Both this technologies are called distributed technologies.
Microsoft System has developed a technology called DOT NET and Su n Micro System has developed a technology called JAVA. Both this technologies are called distributed technologies.
The technology DOT NET will run only on that
operating system’s wh ich are provided by Microsoft
(as on today). Hence DOT NET technology is platform dependent tech nology.
Whereas, the technology called JAVA will run on all operating system’s
irrespective of their providers hence JAVA is called platform independent t
echnology.
The slogan of JAVA is “Write One’s Reuse/Run Anywhere
(WORA)”.
DOT NET technology is not freely downloadable
where as JAVA freely downloadable. DOT NET supports Microsoft developed design
patterns (general designed patterns are not supported) whereas JAVA supports
all the design patterns which are available in IT.
Design
pattern is a predefined and proved rule by third party industry experts to
avoid the receiving problems which are occurring in software development.
JAVA is a distributed technology developed by
James Gosling, Patric Naugton, etc., at Sun Micro System has released lot of
rules for JAVA and those rules are implemented by JavaSoft Inc, USA (which is
the software division of Sun Micro System) in the year 1990. The original name
of JAVA is OAK (which is a tree name). In the year 1995, OAK was revised and
developed software called JAVA (which is a coffee seed name).
JAVA
released to the market in three categories J2SE (JAVA 2 Standard Edition), J2EE
(JAVA 2 Enterprise Edition) and J2ME (JAVA 2 Micro/Mobile Edition).
i. J2SE
is basically used for developing client side applications/programs.
ii. J2EE
is used for developing server side applications/programs.
iii. J2ME
is used for developing server side applications/programs.
If you exchange the data between client and
server programs (J2SE and J2EE), by default JAVA is having on internal support
with a protocol called http. J2ME is used for developing mobile applications
and lower/system level applications. To develop J2ME applications we must use a
protocol called WAP (Wireless Applications Protocol).
FEATURES of java:
- Simple
- Platform independent
- Architectural neutral
- Portable
- Multi threading
- Distributed
- Networked
- Robust
- Dynamic
- Secured
- High performance
- Interpreted Object Oriented Programming Language
1. Simple: JAVA is simple because of the following factors:
i. JAVA is free from pointers hence we can achieve less development time and less execution time [whenever we write a JAVA program we write without pointers and internally it is converted into the equivalent pointer program].
ii. Rich set of API (application protocol interface) is available to develop any complex application.
iii.The software JAVA contains a program called garbage collector which is always used to collect unreferenced (unused) memory location for improving performance of a JAVA program. [Garbage collector is the system JAVA program which runs in the background along with regular JAVA program to collect unreferenced memory locations by running at periodical interval of times for improving performance of JAVA applications.
iii.The software JAVA contains a program called garbage collector which is always used to collect unreferenced (unused) memory location for improving performance of a JAVA program. [Garbage collector is the system JAVA program which runs in the background along with regular JAVA program to collect unreferenced memory locations by running at periodical interval of times for improving performance of JAVA applications.
iv.JAVA contains user friendly syntax’s for developing JAVA applications.
2. Platform Independent:
A program or technology is said to be platform independent if and only if which can run on all available operating systems.
The languages like C, Cpp are treated as platform dependent languages since these languages are taking various amount of memory spaces on various operating systems [the operating system dos understands everything in the form of its native format called Mozart (MZ) whereas the operating system Unix understands everything in its negative format called embedded linking format (elf). When we write a C or Cpp program on dos operating and if we try to transfer that program to Unix operating system, we are unable to execute since the format of these operating systems are different and more over the C, Cpp software does not contain any special programs which converts one format of one operating system to another format of other operating system].
The language like JAVA will have a common data types and the common memory spaces on all operating systems and the JAVA software contains the special programs which converts the format of one operating system to another format of other operating system. Hence JAVA language is treated as platform independent language.
3.Architectural Neutral:
A language or technology is said to be architectural neutral which can run on any available processors in the real world. The languages like C, Cpp are treated as architectural dependent. The language like JAVA can run on any of the processor irrespective of their architecture and vendor.
4. Portable:
A portable language is one which can run on all operating systems and on all processors irrespective their architectures and providers. The languages like C, Cpp are treated as non- portable languages whereas the language JAVA is called portable language.
5. Multi Threading:
Definitions:
1. A flow of control is known as thread.
2. A multi threaded program is one in which there exists multiple flow of controls i.e., threads.
3. A program is said to be multi threaded program if and only of there exists n number of sub- programs. For each and every sub-program there exists a separate flow of control. All such flow of controls are executing concurrently. Such flow of controls is known as threads. Such type of applications is known as multi threading applications.
4. The languages like C, Cpp are treated as threads as single threaded modeling languages (STML). SMTL are those in which there exists single flow of control.
5. The languages like JAVA and DOT NET are treated as multi threadedd modeling languages (MTML). MTML are those in which there exist multiple flows of controls.
6. Whenever we write a JAVA program there exists by default two threads. They are foreground/child thread and background/main/parent thread.
7. A foreground thread is one which always executes user defined sub-programs. In a JAVA program there is a possibility of existing n number of foreground threads.
8. A background thread is one which always monitors the status of foreground thread. In each and every JAVA program tthere exists only one background thread.
9. Hence background thread will be created first and later foreground thread will be created.
6. Distributed:
A service is a said to be a distributed service which runs in multiple servers and that service can be accessed by n number of clients across the globe. In order to develop distributed applications we must require architecture called trusted network architecture. To develop these applications we require a technology called J2EE. Distributed applications are preferred by large scale organizations.
7. Networked:
In real world we have two types of networks. They are un-trusted networks and trusted networks.
Un-trusted networks:
A network is said to be un-trusted network in which there exists n number of inter connected non-autonomous architecture. Un-trusted network is also known as LAN. Using this network architecture, we develop centralized applications. A centralized application is one which runs on single server and it can be access in limited graces. In order to develop centralized.
Trusted network: A network is said to be trusted network in which there exists n number of inter connected
autonomous architecture. Trusted network is also known as WAN. Using this network, we can
develop distributed applications. A distributed application is one which runs on multiple servers
and it can be access in unlimited graces. In order to develop distributed applications we may use
technology called J2EE and these kinds of applications are preferred by large scale
organization.
Installing and setting classpath for java
Let's start our java Installation:
Download Java latest version from oracle. Here i am going to install java 6.0. After downloading Double click on it. The process will start as shown in the below image.
The default folder will select by Java is: C:\Program Files\Java\jdk1.6.0\
Here Select optional features to install from the list below image. You
can change your choice of features after installation by using the
Add/Remove programs utility in the Control Panel. here each Tools having
option to install default feature and optionally sub features will be
installed to local hard drive. you can find it in the above image.
If you don't want to install you can select "Don't install this feature now" option.
Jdk and Jre both will be installed in two steps.
Click on Next button.
Java installation done.
Set Classpath using Commnad Prompt:
Now Let us configure Classpath using Command prompt. Open Run(Win+R) type 'cmd' to open Command prompt.
Create a folder as jprogs under D:\ drive as
D:\cd jprogs
This folder contains your all java programs.
D:\jprogs> set path=%path%;C:\Program Files\Java\jdk1.6.0_26\bin
this tells us the system where to find JDK programs.
Use this command to compile java program:
D:\jprogs\javac HelloWorld.java
After compiling your programs using javac.exe you can see the class file among java file. Then run java file as
D:\jprogs\java HelloWorld
This runs the java interpreter. You should see the program output immediately.If the system cannot find find javac, check the classpath and set correctly. If javac runs but you are getting errors then check your java syntax or text.It may have some spelling mistakes or Capitalization mistakes. Be careful, Java is Case Sensitive.
Make your classpath permanent:
In Windows XP, go to Control Panel, choose "System," click on the "Advanced" tab, click on the "Environment variables" button. In the lower list, "System variables", click on Path:
Click "Edit" and append at the end
;C:\Program Files\Java\jdk1.5.0_09\bin
(or the path to the appropriate folder where the latest version of JDK is installed). Do not put spaces before the appended path string.
Click OK on the path edit box and OK on the Ennvironment Variables box. The new setting will go into effect next time you run Command Prompt.
technology called J2EE and these kinds of applications are preferred by large scale
organization.Installing and setting classpath for java
By seeing this post title you may get doubt. We already installed java and able to run programs also. Why this
again? Actually i got a mail from java beginners like they are getting
some problem while installing java and setting classpath on their
Systems. So just a walk through regarding java installation and Setting
classpath.
Let's start our java Installation:
Download Java latest version from oracle. Here i am going to install java 6.0. After downloading Double click on it. The process will start as shown in the below image.
Click on Next button
If you don't want to install you can select "Don't install this feature now" option.
Set Classpath using Commnad Prompt:
Now Let us configure Classpath using Command prompt. Open Run(Win+R) type 'cmd' to open Command prompt.
Create a folder as jprogs under D:\ drive as
D:\cd jprogs
This folder contains your all java programs.
D:\jprogs> set path=%path%;C:\Program Files\Java\jdk1.6.0_26\bin
this tells us the system where to find JDK programs.
Use this command to compile java program:
D:\jprogs\javac HelloWorld.java
After compiling your programs using javac.exe you can see the class file among java file. Then run java file as
D:\jprogs\java HelloWorld
This runs the java interpreter. You should see the program output immediately.If the system cannot find find javac, check the classpath and set correctly. If javac runs but you are getting errors then check your java syntax or text.It may have some spelling mistakes or Capitalization mistakes. Be careful, Java is Case Sensitive.
Make your classpath permanent:
In Windows XP, go to Control Panel, choose "System," click on the "Advanced" tab, click on the "Environment variables" button. In the lower list, "System variables", click on Path:
Click "Edit" and append at the end
;C:\Program Files\Java\jdk1.5.0_09\bin
(or the path to the appropriate folder where the latest version of JDK is installed). Do not put spaces before the appended path string.
Click OK on the path edit box and OK on the Ennvironment Variables box. The new setting will go into effect next time you run Command Prompt.
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