4.0 change to mehtods

[RichardHightower]

    /**
     * @return true if result is sent successfully.
     */
    boolean success();

    /**
     * @return true if result is sent and this is the last result.
     */
    boolean complete();

    /**
     * If failure is true then cause will not be null.
     *
     * @return true if result is sent and result outcome is a failure.
     */
    boolean failure();

The above should be

    /**
     * @return true if result is sent successfully.
     */
    boolean wasSuccessful();

    /**
     * @return true if result is sent and this is the last result.
     */
    boolean isComplete();

    /**
     * If failure is true then cause will not be null.
     *
     * @return true if result is sent and result outcome is a failure.
     */
    boolean wasFailure();

Work on wording. Look at prior art.