Java Interfaces

interface Fruit {
   public boolean hasAPeel();       
   //has a peel must be implemented in any class implementing Fruit
   //methods in interfaces must be public
}        


interface Vegetable {
   public boolean isARoot();        
   //is a root must be implemented in any class implementing Vegetable
   //methods in interfaces must be public
}  


class FandVUtility {
   static String doesThisHaveAPeel(Fruit fruitIn)
   {
        if (fruitIn.hasAPeel())
           return "This has a peel";
        else   
           return "This does not have a peel";
   }
   static String isThisARoot(Vegetable vegetableIn)
   {
        if (vegetableIn.isARoot())
           return "This is a root";
        else   
           return "This is not a root";
   }   
   static String doesThisHaveAPeelOrIsThisRoot(
     Tomato tomatoIn)
   {
        if (tomatoIn.hasAPeel() && tomatoIn.isARoot())
           return "This both has a peel and is a root";
        else if (tomatoIn.hasAPeel() || tomatoIn.isARoot())
           return "This either has a peel or is a root";
        else   
           return "This neither has a peel or is a root";        
   }
}


class Tomato implements Fruit, Vegetable { 


   boolean peel = false;
   boolean root = false;


   public Tomato() {}   


   public boolean hasAPeel()  
   //must have this method, 
   //  because Fruit declared it
   { 
      return peel; 
   }    
   public boolean isARoot()  
     //must have this method, 
     //  because Vegetable declared it
   { 
      return root; 
   }      


   public static void main(String[] args) {


      //Part one: making a tomato
      Tomato tomato = new Tomato();


      System.out.println(FandVUtility.isThisARoot(tomato));
      //output is: This is not a root
      System.out.println(
        FandVUtility.doesThisHaveAPeel(tomato));
      //output is: This does not have a peel
      System.out.println
        (FandVUtility.doesThisHaveAPeelOrIsThisRoot
          (tomato));
      //output is: This neither has a peel or is a root


      //Part two: making a fruit
      //Fruit  = new Fruit();  
        //can not instantiate an interface like 
        //  this because Fruit is not a class
      Fruit tomatoFruit = new Tomato();   
        //can instantiate by interface like 
        //  this because Tomato is a class


      //System.out.println(
      //  FandVUtility.isThisARoot(tomatoFruit));  
        //can not treat tomatoFruit as a Vegetable 
        //  without casting it to a Vegetable or Tomato
      System.out.println(
        FandVUtility.doesThisHaveAPeel(tomatoFruit));
      //output is: This does not have a peel
      //System.out.println
      //  (FandVUtility.doesThisHaveAPeelOrIsThisRoot
      //  (tomatoFruit)); 
        //can not treat tomatoFruit as a Vegetable 
        //  without casting it to a Vegetable or Tomato
 
   }
}