What is Java?
Java is a computer programming language. It enables programmers to write computer instructions using English based commands, instead of having to write in numeric codes. It’s known as a “high-level” language because it can be read and written easily by humans. Like English, Java has a set of rules that determine how the instructions are written. These rules are known as its “syntax”. Once a program has been written, the high-level instructions are translated into numeric codes that computers can understand and execute.
There are lots of applications and websites that won’t work unless you have Java installed, and more are created every day. Java is fast, secure, and reliable. From laptops to data enters, game consoles to scientific supercomputers, cell phones to the Internet, Java is everywhere.
Types of Java Applications:
Java can be used to develop different types of applications:
• Standalone Applications
• Web Applications
• Distributed Applications
Standalone Applications: A standalone application is a program that runs on your computer. It is more or less like a C or C++ program.
Applets: An applet is an application designed to travel over the Internet and to be executed on the client machine by a Java-Compatible web browser like Internet Explorer or Netscape. Applets are also Java programs but they reside on the servers. An applet cannot be executed like standalone application. Applet can be executed only by embedding it into an HTML page like an image or sound file. To run an applet you need to access an HTML page which has applet embedded into it. When the web browser downloads such an HTML page, it subsequently loads the executable file, which contains Applet and then executes it on the local machine.
Web Applications: Web applications run on the Web Server. Web applications are accessed through web clients i.e. web browsers like Internet Explorer or Netscape. Whenever you access some web site by specifying the URL (Universal Resource Locator), you are accessing some web application. The main components of a web application written in Java are,
• Java Servlets
• Java Server Pages (JSP), and
Java Servlets are also Java programs, which run on the Server and then send the result/response to the client. JSP pages can be thought of as a combination of HTML and Java Code. The Web Server converts JSP pages into Java Servlets before execution.
You access the web application by specifying the URL. If the URL corresponds to an HTML page the web server simply returns the HTML page to the client, which then displays it. If the URL corresponds to the Servlet or JSP then it is executed on the Server and the result/response is returned to the client, which is then displayed by the client.
Distributed Applications: Java application can be divided into a number of modules/components (Java programs), which can run on different machines. The Java programs/applications running on different machines can communicate with each other. To be more precise the Java Objects on one machine can invoke methods on the Java Objects running on another machine. Thus Java has the support for the distributed processing in the language itself.
History of Java:
Java is a programming language developed by Sun Microsystems and published in 1995. Java programming language was originally born out of The Green Project. The project was initiated by Patrick Naughton, Mike Sheridan, James Gosling and Bill Boy along with nine other programmers from Sun Microsystems. To run the project Sun plans to make an operating system built with C + + language. However, James Gosling are not satisfied with the programming language C + + and finally he decided to create its own programming language called Oak. The name was taken from a tree visible from the window of his office. Oak is based on C + + language syntax. But Oak simpler than C + +, more stable and better support network-programming. Moreover Oak made pure object-oriented. Oak language created as a language that is not tied to one platform (cross-platform or multi-platform). At that time the Internet started a new history of the WWW (World Wide Web).
The first GUI browser was Mosaic. Sun saw another gap in the Web world. Sun Oak felt that multi-language platform and is intended for interactive and distributed programming is suitable for the Web. They made the Mosaic as the initial basis for making the first Java browser, later named the Web Runner. In 1995, the name Oak was replaced with the name Java because there is already patented software name. Java name taken from the ground coffee directly pure joy James Gosling. In 1995, java and then became the standard language in the Internet world.