Returns the Component that should receive the focus when a JInternalFrame is selected for the first time. Once the JInternalFrame has been selected by a call to setSelected(true), the initial Component will not be used again. Instead, if the JInternalFrame loses and subsequently regains selection, or is made invisible or undisplayable and subsequently made visible and displayable, the JInternalFrame's most recently focused Component will become the focus owner. The default implementation of this method returns the JInternalFrame's default Component to focus.

frame	the JInternalFrame whose initial Component is to be returned
return	the Component that should receive the focus when frame is selected for the first time, or null if no suitable Component can be found
Throws	IllegalArgumentException: if window is null
See also	getMostRecentFocusOwner