package Ġcom . github . y us aka 3 9 . slack bot . api . handler Ċ Ċ import Ġcom . github . y us aka 3 9 . slack bot . api . entity . Message Ċ Ċ abstract Ġclass ĠHandler Pack Ġ{ ĊĠĠĠ Ġprivate Ġvar Ġ_ received Message : ĠMessage ? Ġ= Ġnull ĊĊĠĠĠ Ġfun Ġset Received Message ( message : ĠMessage ?) Ġ{ ĊĠĠĠĠĠĠĠ Ġthis ._ received Message ?. let Ġ{ ĊĠĠĠĠĠĠĠĠĠĠĠ Ġthrow ĠIllegalStateException (" Received Ġmessage Ġis Ġalready Ġset ") ĊĠĠĠĠĠĠĠ Ġ} ĊĠĠĠĠĠĠĠ Ġthis ._ received Message Ġ= Ġmessage ĊĠĠĠ Ġ} ĊĊĠĠĠ Ġprotected Ġval Ġreceived Message : ĠMessage ĊĠĠĠĠĠĠĠ Ġget () Ġ= Ġthis ._ received Message Ġ?: Ġthrow ĠIllegalStateException (" Backing Ġproperty Ġis Ġnull ") Ċ }