The spec says: "Before switching to a different input method, any currently
uncommitted text is committed."

It is expected that future enhancements will provide for vendor implemented
input methods, including java based input methods. The quoted specification
is implemented in the the input method itself, rather than input context
code. In the future this behavior may not be true, due to differing
input method implementations that may provide alternate user interface behavior.
If this spec is not adjusted, the JCK should test and enforce it.