How do I change the Icon of a program differently from normal methods?

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http://ubuntuforums.org – I installed a program (Netbeans 7.3) from the provider's website (netbeans.org), rather than from the software center (the copy in the software center is outdated and not as stable). For some reason, the program's icon is really pixelized. It shows up in the dash, the launcher, and the desktop normally, but the icon is ugly and annoying because of the really bad quality. I researched how to change a normal program's icon, and I was told several times to go to /usr/share/applications and change the icon of the file in there. However, Netbeans does not show up in that directory. I looked through (Hardware)