listener.java

    /**
     * Add a listener for the state change of the leader with
     * this region.
     * <p>
     * In a special case, if that is a single region environment,
     * then regionId = -1 as the input parameter.
     */
    void addLeaderStateListener(final long regionId, final LeaderStateListener listener);

    /**
     * Add a listener for the state change of the follower with
     * this region.
     * <p>
     * In a special case, if that is a single region environment,
     * then regionId = -1 as the input parameter.
     */
    void addFollowerStateListener(final long regionId, final FollowerStateListener listener);

    /**
     * Add a listener for the state change (leader, follower) with
     * this region.
     * <p>
     * In a special case, if that is a single region environment,
     * then regionId = -1 as the input parameter.
     */
    void addStateListener(final long regionId, final StateListener listener);