我先javac ClassHierarchy.java
   再javac Main.java
   最后 java Main

然后就出现了以下的提示信息:
Exception in thread "main" com.hp.hpl.jena.ontology.ConversionException:Cannot convert node http://www.w3.org/2001/sw/WebOnt/guide-src/food#PotableLiquid to OntClass
      at com.hp.hpl.jena.ontology.impl.OntClassImpl$1.wrap(OntClassImpl.java:73)
      at com.hp.hpl.jena.enhanced.EnhNode.convertTo(EnhNode.java:113)
      at com.hp.hpl.jena.enhanced.Polymorphic.asInternal(Ploymorphic.java:65)
      .......
      at ClassHierarchy.rootClasses(ClassHierarchy.java:183)
      at ClassHierarchy.showHierarchy(ClassHierarchy.java:67)
      at Main.main(Main.java:65)
　
　　我不知道哪里做错了？

运行较慢，需要等等。最后有如下输出结果：
Class vin:WhiteWine
Class vin:WhiteTableWine
Class vin:TableWine
Class vin:WhiteNonSweetWine
Class vin:Loire
Class vin:Bordeaux
  Class vin:Sauterne
Class vin:Region
Class vin:VintageYear
Class vin:Winery
Class vin:WineDescriptor
  Class vin:WineTaste
    Class vin:WineSugar
    Class vin:WineFlavor
    Class vin:WineBody
  Class vin:WineColor
Class vin:SweetWine
Class vin:Semillon
Class vin:SauvignonBlanc
Class vin:RoseWine
Class vin:RedWine
  Class vin:Port
Class vin:RedTableWine
Class vin:ItalianWine
  Class vin:Chianti
Class vin:GermanWine
Class vin:Gamay
Class vin:FullBodiedWine
Class vin:FrenchWine
Class vin:DryWine
Class vin:DryWhiteWine
Class vin:DryRedWine
Class vin:CaliforniaWine
Class vin:TexasWine
Class vin:AmericanWine
Class vin:AlsatianWine
Class food:ConsumableThing
  Class food:EdibleThing
    Class food:Pasta
      Class food:PastaWithWhiteSauce
        Class food:PastaWithLightCreamSauce
        Class food:PastaWithHeavyCreamSauce
      Class food:PastaWithRedSauce
        Class food:PastaWithSpicyRedSauce
        Class food:PastaWithNonSpicyRedSauce
    Class food:OtherTomatoBasedFood
    Class food:NonSweetFruit
    Class food:Meat
      Class food:NonRedMeat
      Class food:RedMeat
        Class food:NonSpicyRedMeat
        Class food:SpicyRedMeat
    Class food:Fowl
      Class food:LightMeatFowl
      Class food:DarkMeatFowl
    Class food:Dessert
      Class food:SweetDessert
      Class food:CheeseNutsDessert
    Class food:SweetFruit
      Class food:Grape
        Class vin:WineGrape
        Class food:EatingGrape
    Class food:Seafood
      Class food:Fish
        Class food:NonBlandFish
        Class food:BlandFish
      Class food:Shellfish
        Class food:OysterShellfish
        Class food:NonOysterShellfish
  Class food:PotableLiquid
    Class vin:Wine
      Class vin:LateHarvest
        Class vin:Sauterne
      Class vin:EarlyHarvest
      Class vin:DessertWine
        Class vin:SweetRiesling
  Class food:MealCourse
  Class food:Meal
Class food:NonConsumableThing
Class food:Wine
Class food:Fruit