2.3.11. White Spaces

The worst hidden thing that can silently happen to a code is a Mix of tabs and spaces. Choose one of them in your code practice, but not both!

Window → Preferences → General → Editors → Text Editors has the relevant choices.

Text editor preferences

The choices are self explanatory.

If you want to quickly enable/disable show white-space, press icon_show_whitespace in the toolbar.