public BST() {
 
    root = null;
    first = null;
    size = 0;
 
  }

    protected Node(K key, V value) {
 
      if ((key == null) || (value == null)) {
 
        throw new NullPointerException();
 
      } else {
 
        this.key = key;
        this.value = value;
        left = null;
        right = null;
        parent = null;
        predecessor = null;
        successor = null;
      };

public V put (K key, V value) {
      if (root == null) {
          root = new Node(key, value);
          if (size == 0) {
                System.out.println("Setting first root!");
                first = root;
          }
          size++;
          System.out.println("Inserted " + root.key);
          root = first;
          System.out.println(size);
          return root.value;
      }
      else {
          int compareKeyToNode = key.compareTo(root.key);
          // Compares key to root's key, returns -1 if less than, 1 if greater than, 0 if keys are equal
          if (compareKeyToNode > 0) {              
              System.out.println("Moved right of " + root.key);
              root = root.right;
          }
          if (compareKeyToNode < 0) {
 
              System.out.println("Moved left of " + root.key);
              root = root.left;
          }
      }
      return (put(key, value));
  }