Only my share

A file hole occurs when the space on disk allocated for a file is less than the file size. Most modern filesystems provide for sparsely populated files, allocating space on disk only for the data actually written (more properly, allocating only those filesystem pages to which data was written). If data is written to the file in noncontiguous locations, this can result in areas of the file that logically contain no data (holes). For example, the following code might produce such kind of file:

import java.nio.ByteBuffer;
import java.nio.channels.FileChannel;
import java.io.File;
import java.io.RandomAccessFile;
import java.io.IOException;

public class FileHole{
     public static void main (String [] argv) throws IOException {
             // Create a temp file, open for writing, and get      
          // a FileChannel         
         File temp = File.createTempFile(“holy”,null);
        RandomAccessFile file = new RandomAccessFile (temp, “rw”);
        FileChannel channel = file.getChannel( );
        ByteBuffer byteBuffer = ByteBuffer.allocateDirect (100);
        putData (0, byteBuffer, channel);             
        putData (5000000, byteBuffer, channel);
        putData (50000, byteBuffer, channel); 

         // there are two holes in this file. This file will

         // not consume 5 MB on disk (unless the filesystem is

         // extremely brain-damaged)

         System.out.println (“Wrote temp file ‘” + temp.getPath( )
                    + “‘, size=” + channel.size( ));

         channel.close( );

        file.close( );

     }

private static void putData (int position, ByteBuffer buffer,
     FileChannel channel) throws IOException {
        
          String string = “*<– location ” + position;
          buffer.clear( );
          buffer.put (string.getBytes (“US-ASCII”));
          buffer.flip( );
          channel.position (position);
          channel.write (buffer);

      }
}

I have read lots of user posting at various pages and none of them would work.
Finally, I found a way to do this correctly and hope this will help to some of you.

Follow the simple steps:

1. To set the environment variables :

echo ‘export JAVA_HOME=/opt/btel/java/jdk1.5.0_16′ > /etc/profile.d/jdk.sh

echo ‘export PATH=$JAVA_HOME/bin:$PATH’ >> /etc/profile.d/jdk.sh

2. You have to source the file you just created by typing:
source /etc/profile.d/jdk.sh

3. Test if Java environment is successfully installed by typing in this in the shell:
java -version

Goes back to 1991, when a group of Sun engineers, led by Patrick Naughton and Sun Fellow (and all-around computer wizard) James Gosling, wanted to design a small computer language that could be used for consumer devices like cable TV switchboxes. Since these devices do not have a lot of power or memory, the language had to be small and generate very tight code. Also, because different manufacturers may choose different central processing units (CPUs), it was important not to be tied down to any single architecture. The project got the code name “Green.”

The requirements for small, tight, and platform-neutral code led the team to resurrect the model that some Pascal implementations tried in the early days of PCs. What Niklaus Wirth, the inventor of Pascal, had pioneered, and UCSD Pascal did commercially, was to design a portable language that generated intermediate code for a hypothetical machine. (These are often called virtual machines—hence, the Java Virtual Machine or JVM.) This intermediate code could then be used on any machine that had the correct interpreter. The Green project engineers used a virtual machine as well, so this solved their main problem.

The Sun people, however, come from a UNIX background, so they based their language on C++ rather than Pascal. In particular, they made the language object oriented rather than procedure oriented. But, as Gosling says in the interview, “All along, the language was a tool, not the end.” Gosling decided to call his language “Oak.” (Presumably because he liked the look of an oak tree that was right outside his window at Sun.) The people at Sun later realized that Oak was the name of an existing computer language, so they changed the name to Java. In 1992, the Green project delivered its first product, called “*7.” It was an extremely intelligent remote control. (It had the power of a SPARCstation in a box that was 6 inches by 4 inches by 4 inches.) Unfortunately, no one was interested in producing this at Sun, and the Green people had to find other ways to market their technology. However, none of the standard consumer electronics companies were interested. The group then bid on a project to design a cable TV box that could deal with new cable services such as video on demand. They did not get the contract. (Amusingly, the company that did was led by the same Jim Clark who started Netscape—a company that did much to make Java successful.)

<!–[if gte mso 9]> Normal 0 false false false EN-US X-NONE X-NONE MicrosoftInternetExplorer4 <![endif]–><!–[if gte mso 9]> <![endif]–> The Green project (with a new name of “First Person, Inc.”) spent all of 1993 and half of 1994 looking for people to buy its technology—no one was found. (Patrick Naughton, one of the founders of the group and the person who ended up doing most of the marketing, claims to have accumulated 300,000 air miles in trying to sell the technology.) First Person was dissolved in 1994.

While all of this was going on at Sun, the World Wide Web part of the Internet was growing bigger and bigger. The key to the Web is the browser that translates the hypertext page to the screen. In 1994, most people were using Mosaic, a noncommercial Web browser that came out of the supercomputing center at the University of Illinois in 1993. (Mosaic was partially written by Marc Andreessen for $6.85 an hour as an undergraduate student on a work-study project. He moved on to fame and fortune as one of the cofounders and the chief of technology at Netscape.) In the SunWorld interview, Gosling says that in mid-1994, the language developers realized that “We could build a real cool browser. It was one of the few things in the client/server mainstream that needed some of the weird things we’d done: architecture neutral, real-time, reliable, secure—issues that weren’t terribly important in the workstation world. So we built a browser.” The actual browser was built by Patrick Naughton and Jonathan Payne and evolved into the HotJava browser that we have today. The HotJava browser was written in Java to show off the power of Java. But the builders also had in mind the power of what are now called applets, so they made the browser capable of executing code inside web pages. This “proof of technology” was shown at SunWorld ‘95 on May 23, 1995, and inspired the Java craze that continues unabated today.

The big breakthrough for widespread Java use came in the fall of 1995, when Netscape decided to make the Navigator browser Java enabled in January 1996. Other licensees include IBM, Symantec, Inprise, and many others. Even Microsoft has licensed Java. Internet Explorer is Java enabled, and Windows ships with a Java virtual machine. (Note that Microsoft does not support the most current version of Java, however, and that its implementation differs from the Java standard.) Sun released the first version of Java in early 1996. It was followed by Java 1.02 a couple of months later. People quickly realized that Java 1.02 was not going to cut it for serious application development. Sure, you could use Java 1.02 to make a nervous text applet that moves text randomly around in a canvas. But you couldn’t even print in Java 1.02. To be blunt, Java 1.02 was not ready for prime time.

The big announcements about Java’s future features trickled out over the first few months of 1996. Only at the JavaOne conference held in San Francisco in May of 1996 did the bigger picture of where Java was going become clearer. At JavaOne the people at Sun Microsystems outlined their vision of the future of Java with a seemingly endless stream of improvements and new libraries.

The big news of the 1998 JavaOne conference was the upcoming release of Java 1.2, which replaces the early toy-like GUI and graphics toolkits with sophisticated and scalable versions that come a lot closer to the promise of “Write Once, Run Anywhere”™ than their predecessors. Three days after (!) its release in December 1998, the name was changed to Java 2.

Since then, the core Java platform has stabilized. The current release, with the catchy name Java 2 Software Development Kit, Standard Edition version 1.3, is an incremental improvement over the initial Java 2 release, with a small number of new features, increased performance and, of course, quite a few bug fixes. Now that a stable foundation exists, innovation has shifted to advanced Java libraries such as the Java 2 Enterprise Edition and the Java 2 Micro Edition.