Credit Card numbers or IMEI in Java (Luhn Algorithm)

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Hans Peter LuhnSome people ask me about how banks or online retailer know when their credit card number is wrong without a regular request or how their mobile services provider or mobile apps know their smartphone or tablet identification(IMEI) are invalid due to initial system configuration manipulation.

What if I tell you the similarity between this identifications and the java code behind the scene?

It sounds really cool, yeah?

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Open Terminal in Nautilus

Nautilus open terminalUbuntu is very cool but in order to be great to programmers and OS administrators I thing it will helpful to add “Open terminal here” option to Nautilus context by right-clicking menu.
The additional benefit over Ctrl+Alt+T shortcut will be a fast way to locate the new terminal prompt in the context of open Nautilus window.

Procedure:
1. Install nautilus-open-terminal package
2. Restart Nautilus

To do this, Open terminal and run:

sudo apt-get install nautilus-open-terminal
nautilus -q

Now you can be able to see “Open in terminal” option on right-clicking.

Note: In Ubuntu 16.04 LTS, this procedure isn’t necessary because Canonical finally include this functionality to the default distro.

Enjoy !.

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How can I remove old kernels/install new ones when /boot is full?

ubuntu-logoSome time ago the Ubuntu 14.04 LTS Software Updater show me this error “Not enough free disk space. The upgrade needs a total of 93.1 M free space on disk ‘/boot’. Please free at least an additional 5,664 k of disk space on ‘/boot’.”

I find it strange that Canonical has removed the solution message of the original text, moreover, when I was searching the command to clean /boot (I had forgotten :-D) I found some caveman procedures, therefore, I going to show you the easy way to remove old kernels to install new ones when /boot is full.

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Video: What’s a computer programmer ?

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VideoI love this video!!!
It’s a short and beautiful presentation about what’s a computer programmer with short interviews with some personalities like Bill Gates, Mark Zuckerberg, Steve Jobs, etc. What although perhaps you are a programmer I recommend you to see it.

Enjoy!!!
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How to Install Oracle Java 8 or 7 in Ubuntu

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In some sitJavauations you need to run applications developed in Oracle Java over Ubuntu.
If you try to do this with recommended open souce flavors like openjdk-8-jdk and/or openjdk-8-jre sometimes rise up errors or malfunctions.

You can correct this situations by installing original Oracle Java Version 7 or 8 doing this procedure in a terminal:
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Ubuntu: How to set a keyboard shortcut for System Monitor

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GNOME System Monitor

GNOME System Monitor

I love Ubuntu but I felt frustrated with the fact it doesn’t have a shortcut to open the GNOME System Monitor like you can do on Windows with CRTL + SHIFT + ESCAPE shotcut to open System Monitor, this is especially good when you have programs like Chrome who likes to consume memory so fast and some times it freeze and you want to kill its processes.

Don’t misunderstand me, I don’t like Windows but actually some little things are more practical.
I going to show you some alternatives:

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