Java - What, Where and Why?
Java technology is wide used currently. Let's start learning of java from basic questions like what is java, where it is used, what type of applications are created in java and why use java?
What is Java?
Java is a programming language and a platform.
Platform Any hardware or software environment in which a program runs, known as a platform. Since Java has its own Runtime Environment (JRE) and API, it is called platform.
Where it is used?
According to Sun, 3 billion devices run java. There are many devices where java is currently used. Some of them are as follows:
1. Desktop Applications such as acrobat reader, media player, antivirus etc.
2. Web Applications such as irctc.co.in, javatpoint.com etc.
3. Enterprise Applications such as banking applications.
4. Mobile
5. Embedded System
6. Smart Card
7. Robotics
8. Games etc.
Types of Java Applications
There are mainly 4 type of applications that can be created using java:
1) Standalone Application
It is also known as desktop application or window-based application. An application that we need to install on every machine such as media player, antivirus etc. AWT and Swing are used in java for creating standalone applications.
2) Web Application
An application that runs on the server side and creates dynamic page, is called web application. Currently, servlet, jsp, struts, jsf etc. technologies are used for creating web applications in java.
3) Enterprise Application
An application that is distributed in nature, such as banking applications etc. It has the advantage of high level security, load balancing and clustering. In java, EJB is used for creating enterprise applications.
4) Mobile Application
An application that is created for mobile devices. Currently Android and Java ME are used for creating mobile applications.
History of Java
Let's see some points that describes the history of java.
· James Gosling, Mike Sheridan, and Patrick Naughton initiated the Java language project in June 1991.
· originally designed for small, embedded systems in electronic appliances like set-top boxes.
· initially called Oak and was developed as a part of the Green project
· In 1995, Oak was renamed as "Java". Java is just a name not an acronym.
· originally developed by James Gosling at Sun Microsystems(which is now a subsidiary of Oracle Corporation) and released in 1995.
· JDK 1.0 released in(January 23, 1996).
Java Version History There are many java versions that has been released.
1. JDK Alpha and Beta (1995)
2. JDK 1.0 (23rd Jan, 1996)
3. JDK 1.1 (19th Feb, 1997)
4. J2SE 1.2 (8th Dec, 1998)
5. J2SE 1.3 (8th May, 2000)
6. J2SE 1.4 (6th Feb, 2002)
7. J2SE 5.0 (30th Sep, 2004)
8. Java SE 6 (11th Dec, 2006)
9. Java SE 7 (28th July, 2011)
Features of Java
There is given many features of java. They are also called java buzzwords.
1.Simple
2.Object-oriented
3.Platform independent
4.Secured
5.Robust
6.Architecture neutral
7.Portable
8.Dynamic
9.Interpreted
10.High Performance
11.Multithreaded
12.Distributed
Simple Java is simple in the sense that:
syntax is based on C++ (so easier for programmers to learn it after C++).
removed many confusing and/or rarely-used features e.g., explicit pointers, operator overloading etc.
No need to remove unreferenced objects because there is Automatic Garbage Collection in java.
Object-oriented Object-oriented means we organize our software as a combination of different types of objects that incorporates both data and behaviour.
Object-oriented programming(OOPs) is a methodology that simplify software development and maintenace by providing some rulues.
Basic concepts of OOPs are:
1. Object
2. Class
3. Inheritance
4. Polymorphism
5. Abstraction
6. Encapsulation
Platform Independent A platform is the hardware or software environment in which a program runs. There are two types of platforms software-based and hardware-based. Java provides software-based platform. The Java platform differs from most other platforms in the sense that it's a software-based platform that runs on top of other hardware-based platforms.It has two components:
1. Runtime Environment
2. API(Application Programming Interface)
Java code can be run on multiple platforms e.g.Windows,Linux,Sun Solaris,Mac/OS etc. Java code is compiled by the compiler and converted into bytecode.This bytecode is a platform independent code because it can be run on multiple platforms i.e. Write Once and Run Anywhere(WORA).
Java technology is wide used currently. Let's start learning of java from basic questions like what is java, where it is used, what type of applications are created in java and why use java?
What is Java?
Java is a programming language and a platform.
Platform Any hardware or software environment in which a program runs, known as a platform. Since Java has its own Runtime Environment (JRE) and API, it is called platform.
Where it is used?
According to Sun, 3 billion devices run java. There are many devices where java is currently used. Some of them are as follows:
1. Desktop Applications such as acrobat reader, media player, antivirus etc.
2. Web Applications such as irctc.co.in, javatpoint.com etc.
3. Enterprise Applications such as banking applications.
4. Mobile
5. Embedded System
6. Smart Card
7. Robotics
8. Games etc.
Types of Java Applications
There are mainly 4 type of applications that can be created using java:
1) Standalone Application
It is also known as desktop application or window-based application. An application that we need to install on every machine such as media player, antivirus etc. AWT and Swing are used in java for creating standalone applications.
2) Web Application
An application that runs on the server side and creates dynamic page, is called web application. Currently, servlet, jsp, struts, jsf etc. technologies are used for creating web applications in java.
3) Enterprise Application
An application that is distributed in nature, such as banking applications etc. It has the advantage of high level security, load balancing and clustering. In java, EJB is used for creating enterprise applications.
4) Mobile Application
An application that is created for mobile devices. Currently Android and Java ME are used for creating mobile applications.
History of Java
Let's see some points that describes the history of java.
· James Gosling, Mike Sheridan, and Patrick Naughton initiated the Java language project in June 1991.
· originally designed for small, embedded systems in electronic appliances like set-top boxes.
· initially called Oak and was developed as a part of the Green project
· In 1995, Oak was renamed as "Java". Java is just a name not an acronym.
· originally developed by James Gosling at Sun Microsystems(which is now a subsidiary of Oracle Corporation) and released in 1995.
· JDK 1.0 released in(January 23, 1996).
Java Version History There are many java versions that has been released.
1. JDK Alpha and Beta (1995)
2. JDK 1.0 (23rd Jan, 1996)
3. JDK 1.1 (19th Feb, 1997)
4. J2SE 1.2 (8th Dec, 1998)
5. J2SE 1.3 (8th May, 2000)
6. J2SE 1.4 (6th Feb, 2002)
7. J2SE 5.0 (30th Sep, 2004)
8. Java SE 6 (11th Dec, 2006)
9. Java SE 7 (28th July, 2011)
Features of Java
There is given many features of java. They are also called java buzzwords.
1.Simple
2.Object-oriented
3.Platform independent
4.Secured
5.Robust
6.Architecture neutral
7.Portable
8.Dynamic
9.Interpreted
10.High Performance
11.Multithreaded
12.Distributed
Simple Java is simple in the sense that:
syntax is based on C++ (so easier for programmers to learn it after C++).
removed many confusing and/or rarely-used features e.g., explicit pointers, operator overloading etc.
No need to remove unreferenced objects because there is Automatic Garbage Collection in java.
Object-oriented Object-oriented means we organize our software as a combination of different types of objects that incorporates both data and behaviour.
Object-oriented programming(OOPs) is a methodology that simplify software development and maintenace by providing some rulues.
Basic concepts of OOPs are:
1. Object
2. Class
3. Inheritance
4. Polymorphism
5. Abstraction
6. Encapsulation
Platform Independent A platform is the hardware or software environment in which a program runs. There are two types of platforms software-based and hardware-based. Java provides software-based platform. The Java platform differs from most other platforms in the sense that it's a software-based platform that runs on top of other hardware-based platforms.It has two components:
1. Runtime Environment
2. API(Application Programming Interface)
Java code can be run on multiple platforms e.g.Windows,Linux,Sun Solaris,Mac/OS etc. Java code is compiled by the compiler and converted into bytecode.This bytecode is a platform independent code because it can be run on multiple platforms i.e. Write Once and Run Anywhere(WORA).
Secured: Java is secured because:
· No explicit pointer
· Programs run inside virtual machine sandbox.
· No explicit pointer
· Programs run inside virtual machine sandbox.
· Classloader- adds security by separating the package for the classes of the local file system from those that are imported from network sources.
· Bytecode Verifier- checks the code fragments for illegal code that can violate accesss right to objects.
· Security Manager- determines what resources a class can access such as reading and writing to the local disk.
These security are provided by java language. Some sucurity can also be provided by application developer through SSL,JAAS,cryptography etc.
Robust Robust simply means strong. Java uses strong memory management. There are lack of pointers that avoids security problem. There is automatic garbage collection in java. There is exception handling and type checking mechanism in java. All these points makes java robust.
Architecture-neutral There is no implementation dependent features e.g. size of primitive types is set.
Portable We may carry the java bytecode to any platform.
High-performance Java is faster than traditional interpretation since byte code is "close" to native code still somewhat slower than a compiled language (e.g., C++)
Distributed We can create distributed applications in java. RMI and EJB are used for creating distributed applications. We may access files by calling the methods from any machine on the internet.
Multi-threaded A thread is like a separate program, executing concurrently. We can write Java programs that deal with many tasks at once by defining multiple threads. The main advantage of multi-threading is that it shares the same memory. Threads are important for multi-media, Web applications etc.
Hello Java Example In this page, we will learn how to write the hello java program. Creating hello java example is too easy. Here, we have created a class named Simple that contains only main method and prints a message hello java. It is the simple program of java.
Requirement for Hello Java Example For executing any java program, you need to
· create the java program.
· install the JDK if you don't have installed it, download the JDK and install it.
· set path of the bin directory under jdk.
· compile and execute the program.
Creating hello java example Let's create the hello java program:
class Simple{
public static void main(String args[]){
System.out.println("Hello Java")
}
}
save this file as Simple.java
To compile:
javac Simple.java
To execute:
java Simple
Output:Hello Java
Understanding first java program Let's see what is the meaning of class, public, static, void, main, String[], System.out.println().
· class is used to declare a class in java.
· public is an access modifier which represents visibility, it means it is visible to all.
· static is a keyword, if we declare any method as static, it is known as static method. The core advantage of static method is that there is no need to create object to invoke the static method. The main method is executed by the JVM, so it doesn't require to create object to invoke the main method. So it saves memory.
· void is the return type of the method, it means it doesn't return any value.
· main represents startup of the program.
· String[] args is used for command line argument. We will learn it later.
· System.out.println() is used print statement.
To write the simple program, open notepad and write simple program as displayed below:
· Bytecode Verifier- checks the code fragments for illegal code that can violate accesss right to objects.
· Security Manager- determines what resources a class can access such as reading and writing to the local disk.
These security are provided by java language. Some sucurity can also be provided by application developer through SSL,JAAS,cryptography etc.
Robust Robust simply means strong. Java uses strong memory management. There are lack of pointers that avoids security problem. There is automatic garbage collection in java. There is exception handling and type checking mechanism in java. All these points makes java robust.
Architecture-neutral There is no implementation dependent features e.g. size of primitive types is set.
Portable We may carry the java bytecode to any platform.
High-performance Java is faster than traditional interpretation since byte code is "close" to native code still somewhat slower than a compiled language (e.g., C++)
Distributed We can create distributed applications in java. RMI and EJB are used for creating distributed applications. We may access files by calling the methods from any machine on the internet.
Multi-threaded A thread is like a separate program, executing concurrently. We can write Java programs that deal with many tasks at once by defining multiple threads. The main advantage of multi-threading is that it shares the same memory. Threads are important for multi-media, Web applications etc.
Hello Java Example In this page, we will learn how to write the hello java program. Creating hello java example is too easy. Here, we have created a class named Simple that contains only main method and prints a message hello java. It is the simple program of java.
Requirement for Hello Java Example For executing any java program, you need to
· create the java program.
· install the JDK if you don't have installed it, download the JDK and install it.
· set path of the bin directory under jdk.
· compile and execute the program.
Creating hello java example Let's create the hello java program:
class Simple{
public static void main(String args[]){
System.out.println("Hello Java")
}
}
save this file as Simple.java
To compile:
javac Simple.java
To execute:
java Simple
Output:Hello Java
Understanding first java program Let's see what is the meaning of class, public, static, void, main, String[], System.out.println().
· class is used to declare a class in java.
· public is an access modifier which represents visibility, it means it is visible to all.
· static is a keyword, if we declare any method as static, it is known as static method. The core advantage of static method is that there is no need to create object to invoke the static method. The main method is executed by the JVM, so it doesn't require to create object to invoke the main method. So it saves memory.
· void is the return type of the method, it means it doesn't return any value.
· main represents startup of the program.
· String[] args is used for command line argument. We will learn it later.
· System.out.println() is used print statement.
To write the simple program, open notepad and write simple program as displayed below:
