package Ġcom . s yle im an . my foot prints . presentation Layer . activities . photo Editor . presenter . state Machine . transitions Stack Ċ Ċ import Ġcom . s yle im an . my foot prints . presentation Layer . activities . photo Editor . presenter . state Machine . States Ċ Ċ /** ĠInterface Ġof ĠTrans itions Stack Ġfor Ġtransitions Ġ*/ Ċ interface ĠI Transitions Stack Extract Ċ { ĊĠĠĠ Ġ/** ĠGet Ġprior Ġstate Ġfor Ġcurrent . ĠReturns Ġnull Ġif Ġprior Ġstate Ġnot Ġfound Ġ*/ ĊĠĠĠ Ġfun Ġfind Prior ( current Ġ: ĠStates ) Ġ: ĠStates ? Ċ }