@Override
    public void setKeyboardSelectionPolicy(final KeyboardSelectionPolicy policy) {
        if (policy == null) {
            throw new NullPointerException("KeyboardSelectionPolicy cannot be null");
        }
        this.keyboardSelectionPolicy = policy;
    }
Get the value that the user selected.

@return the value, or null if a value was not selected
stroom-core-client-widget/src/main/java/com/google/gwt/user/cellview/client/HasDataPresenter.java