How to convert a String to date object in Java

I am going to illustrate using an example

import java.util.Date;
import java.text.SimpleDateFormat;
public class test{
public static void main(String args[]){
String dateStr = "26/08/2010";
SimpleDateFormat formatter = new SimpleDateFormat("dd/MM/yyyy");

try{
Date date = formatter.parse(dateStr);
System.out.println("Date is : " + formatter.format(date));
}
catch (java.text.ParseException e){
e.printStackTrace();
}

}
}

How to use wget to download a file

As i know you cannot download wget to download files from the web sites which needs authentication or human verification.

but most of the times you can directly get the URL of the file,
open a terminal and type (without [])

wget -drc [URL]

if you need to pass from a proxy if you did not set the proxy address yet

 
export http_proxy="[url]:[port]"

example

export http_proxy="http://cache.pdn.ac.lk:3128"

How to clear the page cache memory from terminal

When your page cache memory is full your computer will be really really slow and
you may be unable to run even a single program.

So open a terminal and type as a root user

sync; echo 3 > /proc/sys/vm/drop_caches

This will clear your cache memory and enables you to work faster than previously.

How to add a 'nop' using C

When you write a C code sometimes
you will need to add an assemble nop(No OPeration)
this is how it goes..

__asm__("nop");

for multiple nops add ';'

__asm__("nop;nop;nop");

How to change Grub in ubuntu

Unlike other grub versions, Grub 2 can be edited from the GUI and it is very easy
here is the steps for Ubuntu 10.04,

open a terminal and run

sudo grub update

when the Grub update finished, run

sudo apt-get install 

for this you will need an Internet connection, if not download it from here
now open System->Administration->Startup-Manager

How To Change root password in Ubuntu 10.04

open a terminal and type:

sudo passwd root

then
you will be asked to enter current password or if you did not activate it
already you will be asked for the new password
like this

Enter new UNIX password:
Retype new UNIX password:
passwd: password updated successfully

Cache Timing Attack on AES

in 2005 Daniel Bernstien announced a successful cache timing attack so that from there one can deduce the secret key.. Im working on a project which checks this attack for newer processors.. (core 2 duo and quad core etc..)