The Display Options menu allows you to control how DrJava looks.
Look and Feel: Specify what theme DrJava uses
Toolbar Buttons: Choose the configuration of text and graphics that you want on your toolbar.
Line Numbers: Choose whether you want these shown on the left hand side of the definitions pane.
Window Size and Position: Check this if you want the size and position of the main DrJava window to be saved on exit.
There are two submenus under Display Options, Fonts and Colors.