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Java

An object-oriented programming language from Oracle that is platform independent. Developed by Sun in the early 1990s (Oracle acquired Sun in 2010), and modeled after C++, Java was originally...

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Definition: Java

An object-oriented programming language from Oracle that is platform independent. Developed by Sun in the early 1990s (Oracle acquired Sun in 2010), and modeled after C++, Java was originally designed for embedded applications in set-top boxes and other consumer electronics. Java ignited a revolution when Sun transitioned it to the Web in 1994, and although Java has been reasonably successful on the client (the user's machine), Java on the server became very popular.

When a Java program is launched from a Web page, the program is called a Java "applet." When run without the Web browser on a user's machine, it is a Java "application." When running in a Web server, it is a Java "servlet."

Write Once-Run Anywhere
Java embodies the "write once-run anywhere" model; the Holy Grail of computing for decades. For example, a Java servlet can be moved from a Unix server to a Windows server. Sometimes, a little tweaking is necessary; sometimes a lot, but Java is closer to "write once-run anywhere" than previous development platforms.

This is accomplished by compiling Java source code into an intermediate language called "bytecode." In order to run the bytecode, it is either entirely compiled into machine code and then run or executed a line at a time via the Java interpreter, which is a runtime engine known as the "Java Virtual Machine" (JVM). There are JVMs for all major hardware platforms, and this intermediate bytecode is what makes Java "cross platform," "platform independent" and "write once-run anywhere," all meaning the same thing. When users are asked to update Java from time to time, it is the Java runtime engine that is being updated (see Java Virtual Machine).

Java Vs. JavaScript
Java is not JavaScript. To understand the differences, see JavaScript. For more on Java development environments, see Java platform. See servlet, JSP, Jini, CaffeineMark and caffeine based.

The following Java example of changing Fahrenheit to Celsius is rather wordy compared to the C example in this encyclopedia. Java is designed for GUI-based applications, and several extra lines of code are necessary here to allow input from a terminal.

 import java.io.*;
 class Convert {
  public static void main(String[]args)
  throws IOException {
   float fahr;
   StreamTokenizer in=new
     StreamTokenizer
       (new InputStreamReader(System.in));
   System.out.print("Enter Fahrenheit ");
   in.nextToken();
   fahr = (float) in.nval;
   System.out.println ("Celsius is " +
                        (fahr-32)*5/9);
  }
 }



Java

Java

Java Uses an Intermediate Language
Java source code is compiled into an intermediate language called \"bytecode.\" The bytecode can be run in any hardware that has a Java Virtual Machine (JVM) for that machine platform. Thus, the \"write once-run anywhere\" concept.




Java

Java Runs on Clients and Servers
When a Java program has been called by a Web page from the client machine, it is dubbed an \"applet.\" When it runs on the server, it is known as a \"servlet.\" When running stand alone in a user's computer, it is a Java \"application.\"



Java





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