@startuml

interface Subject{
  attach()
  detach()
  notifyObservers()
}

class TemperatureSensor{
  -observers:ArrayList of Observer
  -tempState:int
  attach()
  detach()
  notifyObservers()
  getTemp()
  setTemp()
}

interface Observer{
update()
}

class AverageDisplay{
 -sum:float
 -count:int
 update()
 display()
}

class NumericDisplay{
 -value:int
 update()
 display()
}

class TextDisplay{
 -value:int
 update()
 display()
}

class MainDriver{
 main()
 }


Subject <|--- TemperatureSensor

TemperatureSensor ---> Observer

Observer <|--- AverageDisplay

Observer <|--- NumericDisplay

Observer <|--- TextDisplay


@enduml