You can select the code you wish, and press SHIFT+TAB until the code lines up to the edge of the screen. You could also go to:
Window->Preferences->general->Editors->Text Editors
and when you're there, specify the tab width under:
Displayed Tab Width.
You can also customize Eclipses' formatter:
Go to:
Window->Preferences->Java->Code Style->Formatter
Select the formatter and press Edit. Edit it to your desire.
Then select the text you wish to format and press Ctrl+Shift+F