Changing editor tab width in eclipse 3.5
Java files have a special place to edit this setting. You need to go to
Window -> Preferences -> Java -> Code Style -> Formatter
And edit the profile.
Check your Java->Code Style->Formatter settings, to see whether you're using tabs or spaces; you might be using spaces!
This setting is superseded for Java by the setting from the Code Style Formatter.
It can be found in Java / Code Style / Formatter (click Edit) / Indentation tab / Indentation
Changing Window -> Preferences -> General -> Editors -> Text Editors tab preference is relevant for text files, not for java files as indicated here. You may create a text file in Eclipse and check that your tab size is really changed.