Java中具有泛型类的树遍历

确切地说，我试图使一棵树变平，并且我一直试图使用泛型函数来获取泛型类中私有属性的值。

我已经附加了这些类，以显示树的确切结构。但是看起来像这样：

  /|\
 1 | 6
  /|\
 5 4 9

我将在最后粘贴我的尝试。首先，让我介绍一下这些类：

三元组只是存储三个相同类型的值。

public class Triple<V> {
    private final V l, m, r;
    public Triple(V l, V m, V r) {
        this.l = l;
        this.m = m;
        this.r = r;
    }
    public V left()   { return l; }
    public V middle() { return m; }
    public V right()  { return r; }
}

简单的界面：

public interface Function<P, R> {
     R apply(P p);
}

现在，上一个棘手的课程。该类型只是一种存储两种类型的值之一的EitherOr，但不能同时存储两种类型的值。

public class EitherOr<A,B> {
    // Constructs a left-type EitherOr
    public static <A> EitherOr left(A a) {
         return new EitherOr(a, null);
    }
    // Constructs a right-type EitherOr
    public static <B> EitherOr right(B b) {
         return new EitherOr(null, b);
    }
    private final A a;
    private final B b;

    private EitherOr(A a, B b) {
         this.a = a; this.b = b;
    }

    public<T> T ifLeft(Function<A,T> f) {
        return f.apply(a);
    }

public<T> T ifRight(Function<B,T> f) {
        return f.apply(b);
    }

    public boolean isLeft() {
        return b == null;
    }
}

我知道这已经很长了，但请忍受。此类实现树结构。

public interface Tree<T> {
    EitherOr<T, Triple<Tree<T>>> get();

    static final class Leaf<T> implements Tree<T> {
           public static <T> Leaf<T> leaf (T value) {
                return new Leaf<T>(value);
           }

           private final T t;

           public Leaf(T t) { this.t = t; }

           @Override
           public EitherOr<T, Triple<Tree<T>>> get() {
                 return EitherOr.left(t);
           }
    }

    static final class Node<T> implements Tree<T> {
         public static <T> Tree<T> tree (T left, T middle, T right) {
             return new Node<T>(Leaf.leaf(left), Leaf.leaf(middle), Leaf.leaf(right));
     }

         private final Triple<Tree<T>> branches;

         public Node(Tree<T> left, Tree<T> middle, Tree<T> right) {
               this.branches = new Triple<Tree<T>>(left, middle, right);
         }

         @Override
         public EitherOr<T, Triple<Tree<T>>> get() {
                 return EitherOr.right(branches);
         }
    }
}

好的。这是我扁平化的想法：

public class MyFlattenTree<T> implements FlattenTree<T> {
    public List<T> flattenInOrder(Tree<T> tree) {
          List<T> list = new ArrayList<T>();
          EitherOr<T, Triple<Tree<T>>> EitherOr;
          EitherOr = tree.get();
          // it is a leaf
          if (EitherOr.isLeft()) {
               // This is where the problem lies
               // I don't how to get the value using a function f
               list.add((T) EitherOr.ifLeft(f));
               return list;
          }
          else {
               // basically recursively go through the tree somehow
          }
          return null;
    }
}

就像我说的那样，我坚持尝试使用Function接口检索EitherOr类中的值。我正在考虑实现Function接口并为“ apply”编写一个仅获取值的函数，但是我不确定如何做到这一点。任何帮助，将不胜感激。谢谢！