Comment afficher une Valeur double avec 2 chiffres aprés la Virgule ?

La classe java.text.DecimalFormat permet de formater une valeur numérique dans le format de son choix en utilisant un pattern dont les symboles principaux sont les suivants :

• 0 permet de représenter un chiffre qui devra obligatoirement être présent, même s'il s'agit d'un zéro inutile.
• # permet de représenter un chiffre en ignorant les zéros inutiles.
• . (le point) permet de représenter le séparateur de la partie décimale.
• , (la virgule) permet de représenter le séparateur des groupes (milliers, millions, etc.).

(vous pouvez vous reporter à la documentation de la classe DecimalFormat pour obtenir la liste complète de tous les symboles).

Format	0	0,02	0,8	12,9
#	0	0	1	13
###	0	0	1	13
0	0	0	1	13
000	000	000	001	013
#.##	0	0,02	0,8	12,9
0.##	0	0,02	0,8	12,9
0.00	0,00	0,02	0,80	12,90
#.00	,00	,02	,80	12,90
#,##0.00	0,00	0,02	0,80	12,90

par exemple :

double ma_Valeur ;
DecimalFormat df = new DecimalFormat("#.##");
System.out.println(df.format(ma_Valeur));

Restore Deleted Files using Git

Sometime you can delete a file  ,by accident, and then you commit your changes . after a while you recognize that you need this file So what you can do ??

what I have tried to resolve such problem (there are several ways) is  this few steps :

1. List all files that have been deleted from my git repository :
   

   git log --diff-filter=D --summary
   
   

2. Search the commit where you deleted your file
3. undo your commit to the searched one BUT don't lose your modifications by taping this cmd :
   

   git reset --soft HEAD~n   
   

   
   n: is the number of undo commit steps


4. if you type  git status  you will re-view your deleted file so to get the file back type this cmd :
   

   git checkout -- [file name]
   

Hope this could helps someone :D

Change Wicket component behavior

Behaviors are kind of plug-ins for Components. They allow functionality to be added to a component and get essential events forwarded by the component. They can be bound to a concrete component (using the bind method which is called when the behavior is attached), but they don't need to. They can modify the components markup by changing the rendered ComponentTag. These are some of them : 

1. AbstractAjaxTimerBehavior

A behavior that generates an AJAX update callback at a regular interval. java doc



WicketComponenet.add(new AbstractAjaxTimerBehavior(Duration.milliseconds(300)){
@Override
protected void onTimer(AjaxRequestTarget target) {
// TODO Auto-generated method stub
System.out.println("ajax here!");
target.add(ComponentToModify);
}});





2. AjaxEventBehavior

An ajax behavior that is attached to a certain client-side (usually javascript) event, such as onClick, onChange, onKeyDown, etc. Example:

WebMarkupContainer div=new WebMarkupContainer(...);
         div.setOutputMarkupId(true);
         div.add(new AjaxEventBehavior("onclick") {
             protected void onEvent(AjaxRequestTarget target) {
                 System.out.println("ajax here!");
             }
         }

This behavior will be linked to the onclick javascript event of the div WebMarkupContainer represents, and so anytime a user clicks this div the onEvent(AjaxRequestTarget) of the behavior is invoked. Java doc


3. AjaxFormComponentUpdatingBehavior

If you have a form component in wicket with some components and you want to change using ajax some things in that form before submit (when you click or edit on one of the components), then you have to use AjaxFormComponentUpdatingBehavior. This is a behavior that updates the hosting FormComponent via ajax when an event it is attached to is triggered.



WicketComponenet.add(new AjaxFormComponentUpdatingBehavior("onchange"){ 
@Override
protected void onUpdate(AjaxRequestTarget target){
// TODO 
System.out.println("ajax here!"); 
target.add(ComponentToModify);
}}.setThrottleDelay(Duration.seconds(1))
);
ComponentToModify.setOutputMarkupId( true );


The key is that your component must be a FormComponent, otherwise the event won't be triggered. Simple components like CheckBox, TextField, DropDownChoice are all FormComponents. Java Doc
you should be careful to set setOutputMarkupId(true) of the component that will be modified after defining the behavior !

Jenkins getting Started

Jenkins Overview

Jenkins Continuous Integration (CI)

server was created to manage and control development lifecycle processes of all kinds, including build, document, test, package, static analysis and many more. Jenkins supports two main functions to help you improve code quality:

Ongoing building and testing

an easy-to-use continuous integration system, Jenkins lets you easily integrate changes to a software project and then automatically initiate a fresh build. By integrating changes as soon as they're ready, you'll find problems sooner, reduce integration conflicts and ensure you always have a working build.

Monitoring the execution of externally-run jobs

Jenkins schedules, monitors and manages externally-run jobs as well, such as cron jobs and procmail jobs and can even handle operations on a remote machine. The tool immediately informs you if something goes wrong, so you can fix the problem right away.

Built-in Automatic Backup

Jenkins lets you define regular backup schedules and control what to back up. Backups can be pushed to a remote server via SFTP or to a local file system. In this way, you configuration will be protected even in case of disaster like disk failures.

Self-upgrade

Upgrading Jenkins to a newer version is really easy. If you choose the native package (such as .deb or .rpm), your package manager will update it automatically. If you choose other installation methods, Jenkins will update itself with a click of a button from GUI.

Jenkins Jobs

in the table you find the list of existant jobs.

Create New Job

you have just to click to new job in the left and the folowing screen will appear.

next give a small description to your job :

Build New Job

After creating your job you can start your build by clicking on Start Build :

Job Configuration

The created jobs must be configured as follow :

Git Configuration

to use Jenkins you have to use a system version Control like Git or svn. If you are using an Http protocol to manage remote repository you need to specify the user credentials in the URL :

http://username:password@ci.opuntia360.com/....

Cron Configuration

the automation build is managed by the peridic Build option. This field follows the syntax of cron (with minor differences). Each line consists of 5 fields separated by TABs or spaces:

MINUTES HOURS JOURMOIS MONTH JOURSEMAINE
MINUTES The minutes in an hour (0-59)
HOURS The hours in a day (0-23)
JOURMOIS the day in a month (1-31)
MONTH The month (1-12)
JOURSEMAINE The day of the week (0-7) where 0 and 7 are Sunday

for example I have so far used Periodic build in jenkins where the schedule:

*/2 * * * * builds the project every 2 minutes

Email Notification

Jenkins offer to you the oportunity to make a post build task.one of the import tasks is mail notification.

Smtp Config

it is very import to configure jenkins to know you smtp server.

Send Email After Build

click to create a post build step and choose "Editable Email Notification" and specify your mail adress.

UBUNTU: HOW TO CHANGE THE COMPUTER NAME (HOSTNAME)

Change Your Computer Name (Ubuntu)

You might run into a situation that requires you to change your (hostname) computer name, either because you need it to meet a naming scheme or you’re just bored with it and want something better. By following these steps, you’ll give your computer a new identity in no time.

1. To get started, press Ctrl – Alt – T on your keyboard to open the Terminal. Next, type the command below to open the hostname file.
2. Type this commande into the terminal and remember that the current computer name is @aymen-Aspire-E1-571

gksu gedit /etc/hostname

3.   Then change the name to whatever you like and save the file.

4. Next, while command console is still open, type the command below to open the hosts file.

gksu gedit /etc/hosts

5. Finally, change the name shown to complete the change and save the file.

6. Close all open windows and restart your system.

After your system has restarted, it will have the new computer name.

Git Over Http

How To use the http protocol to manage git traffic ?

Traditionally git used to work only over ssh or git protocols while there was only a dumb version of git over http which was slow and inefficient.
While this was ok for most of the time sometimes git needs to be able to work over http. 
Now starting from git 1.7 both git servers and clients have support for smart http which works over http(s) and is supposed to be as efficient as the ssh version.

the git-http-backend tool

This functionality is made available by a cgi script called git-http-backend provided with git-core.
So for git to work over http(s) there should be a web server already configured and as a result there won’t be any conflicts by both the web server and git trying acquire port 80.

Configuration

The following steps can be used to configure git to work over http(s) with Apache.

Apache Configuration

Make sure mod_cgi, mod_alias, and mod_env are enabled. to activate the WEBDAV module just use this command :

a2enmod dav_fs

1) Open the Apache config file
2) Append the following. Debian based system should have it under /etc/apache2/apache2.conf by default : SetEnv GIT_PROJECT_ROOT /home/user/git_pub SetEnv GIT_HTTP_EXPORT_ALL ScriptAlias /git/ /usr/lib/git-core/git-http-backend/

The GIT_PROJECT_ROOT should point to the root folder where git repositories would be hosted.

Set this away from the document root of the web server. What the above do is direct any requests with /git/ to the git-http-backend and tell the script that the root of git repositories is GIT_PROJECT_ROOT.
That is all that needs to be done that is specific to git over http(s). The manual for for the git-http-backend explains these steps pretty thoroughly. Now for some tit-bits that are not explained in the manual. Those who are experienced with Apache and Git would find the following very boring.
3) User Righs
For authentication for both read and write accesses append the following to the Apache config file /etc/apache2/apache2.conf :

$  <Location /git>

$  AuthType Basic

$  AuthName “Private Git Access”

$  AuthUserFile /etc/apache2/authusers
 
$  Require valid-user

$  </Location>

What the above do is make requests to /git only accessible to valid users and tell valid users are listed on the file /etc/apache2/authusers. Make sure the file authusers is accessible by Apache. If there is no AuthUserFile in your system the following command can be used to create the user list at /etc/apache2/authusers and add the user ‘username’ to it. The command will prompt for a password for the user :

$ htpasswd -c /etc/apache2/authusers username

4) Restart Apache

On debian most probably :

$ sudo /etc/init.d/apache2 restart

Git Over Http Example

1) Create an empy bare git repository under the specified GIT_PROJECT_ROOT (/home/user/git_pub in our example) :

$ cd to GIT_PROJECT_ROOT
$ mkdir project
$ cd project
$ git init –bare

2) Make the folder ‘project’ and it’s children owned by the user which the web server is run from. This should be done for push requests by clients to work or otherwise the web server won’t be able to merge files.
On debian based systems this user is usually www-data and is defined in a file called envvars under apache2 installation :

$ sudo chown -R www-data project/
$ sudo chgrp -R www-data project/

Now the bare git repository should be pull-able and pushable by authorized users.

3) Clone the git repository over http(s) from another location:

$ git clone http://username@host/git/project

4) Do the first commit:

$ cd project
$ touch readme
$ git add readme
$ git commit -m “first commit”
$ git push origin master

How do I increase the permgen size of Tomcat Server ?

• Increase the Heap size from the catalina.sh file

Tomcat production server sometime will hit the following java.lang.OutOfMemoryError: PermGen space error.

java.lang.OutOfMemoryError: PermGen space
        at java.lang.ClassLoader.defineClass1(Native Method)
        at java.lang.ClassLoader.defineClass(ClassLoader.java:620)
        at java.security.SecureClassLoader.defineClass(SecureClassLoader.java:124)

you should increase the memory by make change in catalina.sh.

Cataline.sh is located at \tomcat folder\bin\catalina.sh

Assign following line to JAVA_OPTS variable and add it into catalina.sh file.

export CATALINA_OPTS="-Xms512m -Xmx1024m"
JAVA_OPTS="-Djava.awt.headless=true -Dfile.encoding=UTF-8 
-server -Xms2536m -Xmx2536m
-XX:NewSize=256m -XX:MaxNewSize=1024m -XX:PermSize=1536m 
-XX:MaxPermSize=1536m -XX:+DisableExplicitGC"

• Increase the Heap size from the the Eclipse IDE

if you are using tomcat sever with eclipse you need to resolve this exception by modifying the tomcat arguments :

If you see java.lang.OutOfMemoryError: PermGen space errors, you need to increase the permanent generation space available to Eclipse.

PermGen is the permanent generation of objects in the VM (Class names, internalized strings, objects that will never get garbage-collected). An easy, if somewhat memory-hungry fix is to enlarge the maximum space for these objects by adding

• double click on the tomcat server
• Click to Open Launch Configuration

• Choose the Arguments tab and add the following parameters

     -Xms1024m -Xmx1024m -XX:PermSize=1024m -XX:MaxPermSize=1024m

• Be Careful !!!!

you have to be careful when increasing the heap size of your tomcat server and jvm.

 As you can see, if you allocate a large Java Heap (2 GB+) for a 32-bit JVM process, the native memory space capacity will be reduced automatically, opening the door for JVM native memory allocation failures.
you will get the following exception :OutOfMemoryError: unable to create new native thread

For a 64-bit JVM process, your main concern, from a JVM C-Heap perspective, is the capacity and availability of the OS physical, virtual and swap memory.
 What you will learn shortly is that this JVM problem is very often related to native memory depletion; either at the JVM process or OS level. For now please keep in mind that:

• A 32-bit JVM process is in theory allowed to grow up to 4 GB (even much lower on some older 32-bit Windows versions).

• For a 32-bit JVM process, the C-Heap is in a race with the Java Heap and PermGen space e.g. C-Heap capacity = 2-4 GB – Java Heap size (-Xms, -Xmx) – PermGen size (-XX:MaxPermSize)

• A 64-bit JVM process is in theory allowed to use most of the OS virtual memory available or up to 16 EB (16 million TB)