From the current spec "Not all platforms ... support input methods."

The InputContext APIs need to specify their behavior in this case.
I believe the following APIs are affected:

selectInputMethod(Locale): suggest add
"If a platform does not support input methods, then false will always be returned."

dispatchEvent(AWTEvent): suggest add
"If a platform does not support input methods, then the event will never
be consumed."

endComposition()
setCharacterSubsets()
dispose(), suggest the following;
"If a platform does not support input methods, then the above methods have no effect."

getInputMethodControlObject(), suggest the following:
"If a platform does not support input methods, then null is returned.