I am trying to adjust the width of tabs from Window -> Preferences -> General -> Editors -> Text Editors where there is a field for "Display Tab Width". But no matter what I enter there the size of indentations when I start a newline in a Java file is 4. Any ideas?
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.