@startuml
package com.iluwatar.visitor {
  class Commander {
    + Commander(children : Unit[])
    + accept(visitor : UnitVisitor)
    + toString() : String
  }
  interface UnitVisitor {
    + visitCommander(Commander) {abstract}
    + visitSergeant(Sergeant) {abstract}
    + visitSoldier(Soldier) {abstract}
  }
  class CommanderVisitor {
    + CommanderVisitor()
    + visitCommander(commander : Commander)
    + visitSergeant(sergeant : Sergeant)
    + visitSoldier(soldier : Soldier)
  }
  class Soldier {
    + Soldier(children : Unit[])
    + accept(visitor : UnitVisitor)
    + toString() : String
  }
  class App {
    + App()
    + main(args : String[]) {static}
  }
  abstract class Unit {
    - children : Unit[]
    + Unit(children : Unit[])
    + accept(visitor : UnitVisitor)
  }
  class SoldierVisitor {
    + SoldierVisitor()
    + visitCommander(commander : Commander)
    + visitSergeant(sergeant : Sergeant)
    + visitSoldier(soldier : Soldier)
  }
  class SergeantVisitor {
    + SergeantVisitor()
    + visitCommander(commander : Commander)
    + visitSergeant(sergeant : Sergeant)
    + visitSoldier(soldier : Soldier)
  }
  class Sergeant {
    + Sergeant(children : Unit[])
    + accept(visitor : UnitVisitor)
    + toString() : String
  }
}
Commander --|> Unit 
CommanderVisitor ..|> UnitVisitor 
Soldier --|> Unit 
SoldierVisitor ..|> UnitVisitor 
SergeantVisitor ..|> UnitVisitor 
Sergeant --|> Unit 
@enduml