package Ġcom . hop ovo . mobile . android . prep exam . data . exercise . source Ċ Ċ import Ġcom . hop ovo . mobile . android . prep exam . model . exercise . Exercise Ċ import Ġio . reactivex . Comp letable Ċ import Ġio . reactivex . Observable Ċ import Ġio . reactivex . Single ĊĊ Ċ interface ĠExercise DataStore Ġ{ ĊĊĠĠĠ Ġfun Ġsave Exercise ( exercise : ĠExercise ): ĠComp letable ĊĊĠĠĠ Ġfun Ġget Exercise ById ( id Exercise : ĠInt ): ĠObservable < Exercise > ĊĊĠĠĠ Ġfun Ġget Exercise (): ĠObservable < List < Exercise >> ĊĊĠĠĠ Ġfun ĠisValid Cache (): ĠSingle < Boolean > ĊĊĠĠĠ Ġfun Ġset Last Cache Time ( last Cache : ĠLong ) Ċ } Ċ