Code on Blog

Linux Tip 4

2008-02-08T01:22:00.000-08:00

This is a simple bash script that will shut down your computer.All you have to do is to open a text editor( such as gedit,vi,emacs or whatever your favorite is) write the code than save it as "theName.sh". Inside the file write "init 0" (for shutdown) or "init 6" (for reboot).Then place this in the /usr/bin/ directory. Now you can open a console window and call the "theName"(watch out for case) script.

Java screenshot

2008-01-15T14:23:00.000-08:00

This is a simple class that takes a screenshot and saves the image as a jpeg file.

screenshot.java :

import java.awt.AWTException;
import java.awt.Rectangle;
import java.awt.Robot;
import java.awt.image.BufferedImage;
import java.io.File;
import java.io.IOException;

import javax.imageio.ImageIO;

public class screenshot {
int k;
public screenshot(){
k=0;
}
public void takeScreenShot() {

try {

Robot robot = new Robot();
BufferedImage bi=robot.createScreenCapture(new Rectangle(1024,768));
ImageIO.write(bi, "jpg", new File("E:\\PROJECTS\\Java Stuff\\My new Projects\\film\\imageTest"+k+".jpg"));
k++;
} catch (AWTException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
}
}
}

In the other class you first create an instance of the screenshot class like this :
screenshot x=new screenshot();

Then we call the function:
x.takeScreenshot();

and a picture is saved into the folder defined earlier.

This is the code of the recording.java class.
import javax.swing.*;
import java.awt.*;
import java.awt.event.*;
public class recording implements Runnable {
screenshot x=new screenshot();
Thread th;
public static void main(String args[])
{
new recording();
}
public recording()
{
th=null;
start();
}

public void start()
{
if (th==null)
{
th=new Thread(this);
th.start();
}
}

public void run()
{
while(th!=null)
{
x.takeScreenShot();
try
{
Thread.sleep(1000);
}
catch(InterruptedException e)
{
System.out.println(e);
}
}
}

public void stop()
{
}
}

This small java application takes a screenshot every second and saves it in your computer.If you want to capture all the action that takes place on your screen you can lower the 1000 miliseconds timeout.That will generate lots of images though :D
You can use this trick in many ways.You can spy on someone that chats on your pc ;), you can take screenshots of you playing some game and I will just let you think about others ... Hope you will find this useful !

Linux Tip 3

2008-01-08T14:12:00.000-08:00

The find command is very useful in a unix environment when one needs to find a certain category of files.For example if you have to find all the files and folders that match a pattern you can use it like that :
find /ThePathToTheSearchedDirectory -name 'picture*'
This way you can find all the files that start with 'picture'. You can find files like
picture01.png , picture02.png, picture03.png ... and you can take further actions on them.
The find command is far more complex than that.In order to learn more about a command use the man command :
Examples:

man find
man grep
etc.

Java 4K Programming Contest

2008-01-08T10:00:00.000-08:00

First of all : Happy new year !
Java4k is a very funny contest . The best part is that you don't have to write 3 months to create a decent entry. You could create a nice game (that has to be under 4 kilobytes in size !!!) in a single night .All you have to do is to respect the rules and create a fun game.Even if you won't write a game you can just look at the other games an have tons of fun playing those small unique games.
Here is the announcement :
The Java 4K Programming Contest is the ultimate byte-squeezing Java challenge! Using only 4096 bytes, competitors use every trick up their sleeve to create an entire game.

Submit your games here before March 1st, 2007!

Contest Prizes
* 6 months free playtime of Wurm Online, courtesy of Mojang Specifications!
* Top 5 entries score a free copy of Tribal Trouble, courtesy of Oddlabs!

Basic rules are as follows:
* The final game package (byte code + resources) must be below or equal to 4096 bytes

* Must be a playable game (cannot be a pointless animation)

* Must be pure Java (no JNI)

* Must be self-contained- no external resources (e.g. loading an image from a website)

* No Pack200

* No external libraries may be used - you must use the libraries that come with the “public” version of the JRE

* No soundbanks may be used because they are not a default part of the “public” JRE. You will have to create your sounds at runtime rather than use MIDIs.

* The presentation (jar, class, or other) does not matter, as long as the code can be executed without a command line

* The target JRE is 1.5 (Java 5) or lower

Specific questions and comments can be made at the official Java 4K forum.

Official website

Good luck ;) !

Merry Christmas !

2007-12-24T11:19:00.000-08:00

Code-on-Blog wishes you a very merry Christmas !

C++ challenge answer !

2007-12-19T14:46:00.000-08:00

Remember the last C++ challenge question ? Here is the answer. It's C++ challenge not C :D.Wonder why ? Well all you have to do is to comment/delete the stdio.h inclusion.This makes the printf function an undeclared function, which you declare :D.The printing is done by using the cout function ;).

#include iostream.h
//#include stdio.h
void printf(char *c,int x)
{
cout<<"Nice trick, eh ? :)";
}
int main()
{
int a=100,b=30;
printf("%d",a+b);
return 0;
}

Doesn't sound that hard now,right ? :)

Linux Tip 2

2007-12-17T13:16:00.000-08:00

One of the most used command in unix is cd , meaning "change directory".
To change your directory to an absolute path you have to write this : cd /root/whatever . If you want to change to a relative path you have to execute something like this : cd ./dir3/dir5 . The added dot at the beginning represents the current directory, and the rest of the command represents the path relative to the current directory. You can also skip the "." part and just write cd dir3/dir5.But must not begin with "/" ! If you do so then it will be an absolute path ! To find out the current directory while in linux(or any other unix flavor) you can type : pwd (print working directory).

This commands will help you navigate through your filesystem.

C++ challenge question

2007-12-15T23:36:00.000-08:00

This question was given at some interviews. You have this code :
#include stdio.h
/*You have to put stdio.h between "<" and ">" , as I wasn't able to post that :)*/
int main()
{
int a=100,b=30;
printf("%d",a+b);
return 0;
}

Without modifying the main function, can you make the program print "I am no longer unemployed :) " ? Good Luck ! Answer coming in 2 or 3 days :) .

Linux Tip

2007-12-09T15:01:00.000-08:00

I will post this kind of tips every few days. So.. How do you find out how much space do you have left on your disks when using linux ? You open a terminal window, and you execute the following command : df . This will output the total space you have left on each mounted filesystem.

Hello World !

2007-12-08T07:58:00.000-08:00

Here is the the classic "Hello World !" application that I've promised to you :). This one prints "Hello World !" on your console.

First download and install tha Java development Kit from here : http://java.sun.com/javase/downloads/index.jsp

Make sure you installed it right like this :Click Start->run

Then write "cmd" and press enter. In the console window write "java -version" and press enter again. If you don't get an error then you made the first step :).

Download and install an IDE(Integrated Development Environment) or simpler : "the program where you write the code".Here are some choices :

Eclipse (big IDE written in java)-it's great but it's pretty big so you need a strong computer for it. Take it from here :http://www.eclipse.org/

Netbeans(big IDE written in java)-same as at Eclipse. You might have installed the JDK with bounded with this one. If not get it from here : http://www.netbeans.org/

JCreator(written in C++)-small and fast.It's a commercial software but you can install the free version of it. It's more than enough for beginning.Here it is : http://jcreator.com/

Now create a file called HelloWorld.java ,open it from the IDE and copy this code there :

public class HelloWorld{

 
 public   static void main( String[] args ){

  System.out.println( "Hello world" );

}
}

Save it. Now you might be able to compile and run it. If you are not then you might need to configure your IDE or just use the command line mode of compiling.

Place your file in a directory (lets say c:\java\source\).

Open a command prompt (Start->run+"cmd" +Enter,remember ? :) )

Write :

cd c:\java\source

"c:\Program Files\jdk1.6.0_03\bin\javac" HelloWorld.java

You might need to change the your path ( c:\Program Files\jdk1.6.0_03\ ) to where the jdk is installed.
Now you just compiled your first java program. All you have to do now is run it .In the same console window write :

java HelloWorld

(must be HelloWorld not HelloWorld.java)

This will output Hello World !

Congratulations you just finished your first java program.

Now try to change your source code then save,compile and run to see what happens.

Change this

System.out.println( "Hello world" );

System.out.println( "The text changed :) " );

run it.

Try this then.

System.out.println( "Hello "+"World !");

Then change it to this

System.out.println( "1+3="+(1+3) );

That's all. Hope you enjoyed it !

The Java programming language

2007-12-07T09:43:00.000-08:00

Write once, run everywhere !

Many know what java is . If you don't there's no need to panic. You will soon learn the concept of java.

Java is a programming language released in 1995 by Sun Microsystems . Most of it's syntax derives from C and C++ but is a higher level programming language.Higher level doesn't mean that it's better,it only means that it's used for things such as desktop,web applications , not for programming drivers or operating systems such as Windows and Linux . Java applications are compiled to bytecode which can run on any Java virtual machine (JVM) regardless of the operating system or computer architecture.

Java is not as fast as C++(because C++ is a compiled language) , but is not as slow as python (because python is an interpreted language) . The advantage of using it over faster languages is that it's syntax is very clear, it is an Object Oriented Programming (OOP) language, it's fast enough to be used in most cases, It's mostly PORTABLE (big advantage in some cases) and because you won't have to deal with low level stuff, the time required to develop an application is greatly reduced.

I already said too much so the next post will teach you how to write a simple program in java.

Welcome to Code-on-Blog

2007-12-07T09:33:00.000-08:00

Hey there ! This is the first post on Code-on-Blog :D ! Obviously this site will be about coding(a.k.a. programming) in different languages. Some tuturials will come soon ;) . Enjoy them !