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This setting is superseded for Java by the setting from the Code Style Formatter.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.