TreeNode implements Iterable<TreeNode<T>>, Serializable, Cloneable { public long size() { if (isLeaf()) { return 1; } final long[] count = {0}; TraversalAction<TreeNode<T>> action = new TraversalAction<TreeNode<T>>() { @Override public void perform(TreeNode<T> node) { count[0]++; } @Override public boolean isCompleted() { return false; } }; traversePreOrder(action); return count[0]; } TreeNode(T data);  TreeNode(); abstract Collection<? extends TreeNode<T>> subtrees(); abstract boolean add(TreeNode<T> subtree); abstract boolean dropSubtree(TreeNode<T> subtree); abstract void clear(); abstract TreeNodeIterator iterator(); T data(); void setData(T data); boolean isRoot(); TreeNode<T> root(); TreeNode<T> parent(); boolean isLeaf(); @SuppressWarnings("unchecked") TreeNode<T> find(final T data); Collection<? extends TreeNode<T>> findAll(final T data); boolean hasSubtree(TreeNode<T> subtree); boolean contains(TreeNode<T> node); boolean containsAll(Collection<TreeNode<T>> nodes); boolean remove(TreeNode<T> node); boolean removeAll(Collection<TreeNode<T>> nodes); void traversePreOrder(TraversalAction<TreeNode<T>> action); void traversePostOrder(TraversalAction<TreeNode<T>> action); Collection<TreeNode<T>> preOrdered(); Collection<TreeNode<T>> postOrdered(); Collection<? extends TreeNode<T>> path(TreeNode<T> descendant); TreeNode<T> commonAncestor(TreeNode<T> node); boolean isSiblingOf(TreeNode<T> node); boolean isAncestorOf(TreeNode<T> node); boolean isDescendantOf(TreeNode<T> node); long size(); int height(); int level(); @SuppressWarnings("unchecked") @Override TreeNode<T> clone(); @SuppressWarnings("unchecked") @Override boolean equals(Object obj); @Override int hashCode(); @Override String toString();  }
@Test public void testSize() { String message = "Tree node size was incorrectly calculated"; assertSame(message, 1L, node6.size()); assertSame(message, 2L, node9.size()); assertSame(message, 4L, node3.size()); assertSame(message, 11L, root.size()); }