how to set default jre

sudo update-alternatives --config java


one sentence work out . Awesome!

i love ubuntu!
there are some commands show information about jre ,jdk.


sudo update-java-alternatives
and you can add some param to show .
for example:

william@william-superstar:/VirtualWorld/eclipse$ sudo update-java-alternatives -l
[sudo] password for william:
java-6-sun 63 /usr/lib/jvm/java-6-sun

how to uninstall eclipse java compiler

sudo apt-get remove --purge java-gcj-compat

if you wanna intall sun jdk so type this command
sudo apt-get install sun-java6-jdk

ubuntu install realplayer

.rpm and .bin are supported in official website http://www.real.com/linux.
i use alien install realplayer.rpm ,it seems to should to config script ,and when installed ,it donnot work.
so .bin is success .
sudo chmod +x Realplayer11GOLD.bin
./bin Realplayer11GOLD.bin

then like this:
william@william-superstar:~/Desktop$ ./../RealPlayer/RealPlayer11GOLD.bin
Extracting files for Helix installation........................

Welcome to the RealPlayer (11.0.0.4028) Setup for UNIX
Setup will help you get RealPlayer running on your computer.
Press [Enter] to continue...


Enter the complete path to the directory where you want
RealPlayer to be installed. You must specify the full
pathname of the directory and have write privileges to
the chosen directory.
Directory: [/home/william/Desktop/RealPlayer]: /home/william/RealPlayer/

You have selected the following RealPlayer configuration:

Destination: /home/william/RealPlayer/

Enter [F]inish to begin copying files, or [P]revious to go
back to the previous prompts: [F]: F

Copying RealPlayer files...No write-permission to /etc/profile.d ...skip.
.Succeeded.
installing application icons resource...
installing document icons resource...
..........Succeeded.
.Configuring Mozilla...
Installing .mo locale files...
Setting selinux context...
/usr/share or /usr/bin no write-permission...skip.

RealPlayer installation is complete.
Cleaning up installation files...
Done.


now ,you should goto the directory where you install the .bin .and run the realplayer in terminal.
like following:
william@william-superstar:~/RealPlayer$ ls
Bin common install.log mozilla postinst realplay RealPlayer11GOLD.bin
codecs doc LICENSE plugins README realplay.bin share
william@william-superstar:~/RealPlayer$ ./realplay

edit system file

graphical provide us the drag and drop ways to deal with files.but cause of the user permission control ,it always disappoint you.for example:u wanna move a file from /media/windowpartion to / .in command line ,it is no big deal .sudo mv /media/windowpartion / is enough.but if u wanna change graphically, maybe the popup alert will tell you: you request are denied. what we can do?
follow me :
if you are kde ,i mean ,kubuntu,type following command:
kdesudo konqueror
actually, here kongqueror is not a brower,but file manager system.now ,you can use it edit the file belongs to root.cause there is kdesudo when you run konqueror ,remenber?
if Ubuntu (Gnome)
gksudo nautilus
if dont take effect.type ATL+F2 and come into command mode,
then type:
gksudo nautilus
this would work
if Xubuntu (XFCE)
type :
gksudo thunar


at last but not least: Good luck!

Vista Ubuntu grub Boot

It is a cool thing to install dual OS -windows and linux(or unix ).
As we know ,if u guy wanna install multi-boot systems ,u should first install windows and then linux. linux have 2 loader tools--lilo and grub.Actually ,i prefer grub ,more powerful and flexibly.

Ok till now ,everthing goes fine .but if my windows crash down,and i reinstall it ,finnaly u find you the grub is missing and you have no choise but enter windows.
so how to reinstall grub when you windows wipe it out?
follow me!
first step:
insert your Ubuntu CD,then boot form live cd .i mean ,you run the option: "try ubuntu without any change to your computer".
after that you will enter ubuntu system.and open the terminal(console is also ok,hehe )
second step:
enter following commonds:
sudo grub
find /boot/grub/stage1
(then the output will be like this: (hd*,*) )
root (hd*,*)
setup (hd0)
quit


then restart your computer .congratulations!
ps:sometimes u also find the grub do not contains the windows items.so you should edit
/boot/grub/menu.lst（note:i donot do this in person ,if this donot work .check it out in google ）
and add something like that:
# This entry automatically added by the Debian installer for a non-linux OS
# on /dev/sda1
title Microsoft Windows XP Home Edition
root (hd0,0)
savedefault
makeactive
chainloader +1



双系统,windows崩溃，重装系统后 grub启动菜单丢失此时修复的方式为：
1 插入光盘（如果没有光盘的话那就有点困难了）
2 以 live cd 方式启动，进入系统(如果你的系统是8.0的那么就是第一个选项)
3 打开终端输入下面的命令
sudo grub
find /boot/grub/stage1
4然后会有这样的输出：（hd*,*）
5接着输入下面的命令：
root (hd*,*) 注：也就是上面的输出
setup （hd0）
quit
6重启之后就可以进入Ubuntu 了
ＰＳ:优势发现无法进入windows。此时可以在 /boot/grub/menu.lst 加入如下内容
(这个我没有亲手试过，如果不行可以再在google上看下)

# This entry automatically added by the Debian installer for a non-linux OS
# on /dev/sda1
title Microsoft Windows XP Home Edition
root (hd0,0)
savedefault
makeactive
chainloader +1

Ubuntu Resolution

you know what ? this damn problem really piss me off .
and finally i fix it.
problem: the max resolution is 800*600
reason:nvidia (if this is your video card type),you should manually install it . find the
hardware item ,and then choose enable it .then have a cup of coffee,Ubuntu will do the rest ........
Hulla

hibernate configuration

when you config hibernate application,make sure you have import the following 9 jars:
c3p0.jar,cglib.jar,commons-collection.jar,dom4j.jar,commons-logging,jar
asm.jar,antlr.jar.actually,the names of the jars is not precise.no version.but it is ok.
then you should config the configuration files.hibernate.cfg.xml,log4j.properties,and *.hbm.xml