If you try the City Input Method example in the following document:

http://javadesktop.org/articles/InputMethod/index.html

A NullPointerException gets thrown if you scroll up above number "1 San Francisco..." using the arrow keys in the "Lookup Window" with the city names.

---------------------------------
Exception in thread "AWT-EventQueue-0" java.lang.NullPointerException
       at com.sun.demos.cityim.internal.CityInputMethod.formatOutput(CityInputM
ethod.java:741)
       at com.sun.demos.cityim.internal.CityInputMethod.sendText(CityInputMetho
d.java:755)
       at com.sun.demos.cityim.internal.CityInputMethod.selectCandidate(CityInp
utMethod.java:799)
       at com.sun.demos.cityim.internal.CityInputMethod.dispatchEvent(CityInput
Method.java:333)
       at sun.awt.im.InputContext.dispatchEvent(InputContext.java:238)
       at sun.awt.im.InputMethodContext.dispatchEvent(InputMethodContext.java:1
80)
       at java.awt.Component.dispatchEventImpl(Component.java:3902)
       at java.awt.Container.dispatchEventImpl(Container.java:2024)
       at java.awt.Component.dispatchEvent(Component.java:3803)
       at java.awt.KeyboardFocusManager.redispatchEvent(KeyboardFocusManager.ja
va:1810)
       at java.awt.DefaultKeyboardFocusManager.dispatchKeyEvent(DefaultKeyboard
FocusManager.java:672)
       at java.awt.DefaultKeyboardFocusManager.preDispatchKeyEvent(DefaultKeybo
ardFocusManager.java:920)
       at java.awt.DefaultKeyboardFocusManager.typeAheadAssertions(DefaultKeybo
ardFocusManager.java:798)
       at java.awt.DefaultKeyboardFocusManager.dispatchEvent(DefaultKeyboardFoc
usManager.java:636)
       at java.awt.Component.dispatchEventImpl(Component.java:3841)
       at java.awt.Container.dispatchEventImpl(Container.java:2024)
       at java.awt.Window.dispatchEventImpl(Window.java:1774)
       at java.awt.Component.dispatchEvent(Component.java:3803)
       at java.awt.EventQueue.dispatchEvent(EventQueue.java:463)
       at java.awt.EventDispatchThread.pumpOneEventForHierarchy(EventDispatchTh
read.java:242)
       at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThre
ad.java:163)
       at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:157)

       at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:149)

       at java.awt.EventDispatchThread.run(EventDispatchThread.java:110)