Requests that this Component get the input focus, and that this Component's top-level ancestor become the focused Window. This component must be displayable, focusable, visible and all of its ancestors (with the exception of the top-level Window) must be visible for the request to be granted. Every effort will be made to honor the request; however, in some cases it may be impossible to do so. Developers must never assume that this Component is the focus owner until this Component receives a FOCUS_GAINED event. If this request is denied because this Component's top-level Window cannot become the focused Window, the request will be remembered and will be granted when the Window is later focused by the user.
This method cannot be used to set the focus owner to no Component at all. Use KeyboardFocusManager.clearGlobalFocusOwner() instead.
Because the focus behavior of this method is platform-dependent, developers are strongly encouraged to use requestFocusInWindow when possible.
Note: Not all focus transfers result from invoking this method. As such, a component may receive focus without this or any of the other {@code requestFocus} methods of {@code Component} being invoked.
@see #requestFocusInWindow
@see java.awt.event.FocusEvent
@see #addFocusListener
@see #isFocusable
@see #isDisplayable
@see KeyboardFocusManager#clearGlobalFocusOwner
@since JDK1.0