Given:
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interface IFamTree{
}

class Unknown implements IFamTree{
  Unknown(){
  }
}

class Person implements IFamTree{
  String name;
  IFamTree mother;
  IFamTree father;

  Person (String name, IFamTree mother, IFamTree father){
   this.name = name;
   this.mother = mother;
   this.father = father;
  }
}

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Design a Java method countGens that counts the number of
generations in a family tree

interface IFamTree{
  int countGens();
}

// in Unknown...

// produces the number of generations in this empty family tree
public int countGens(){
  return 0;
}

// in Person...

// produces the number of generations in this person's family tree
// (I want them to use an if-statement here instead of using a max function)
public int countGens(){
  if (this.father.countGens() > this.mother.countGens())
     return 1 + this.father.countGens();
  else
     return 1 + this.mother.countGens();
}