BinaryTree.java

package tree;

import java.util.Iterator;
import java.util.Stack;

/**
 * BinaryTree implementation.
 */
public class BinaryTree<T> implements Iterable<BinaryTree<T>>{
    private TreeNode<T> root;

    public BinaryTree() {}

    public BinaryTree(T data) {
        createLeaf(data);
    }

    public BinaryTree(BinaryTree<T> left, T data, BinaryTree<T> right) {
        createLeaf(data);
        addSubLeft(left);
        addSubRight(right);
    }

    public void createLeaf(T data) {
        root = new TreeNode<T>(data);
    }

    public void addSubLeft(BinaryTree<T> tree) {
        root.leftTree = tree;
    }

    public void addSubRight(BinaryTree<T> tree) {
        root.rightTree = tree;
    }

    public T element() {
        return root.data;
    }

    public BinaryTree<T> left() {
        return root.leftTree;
    }

    public BinaryTree<T> right() {
        return root.rightTree;
    }

    public boolean empty() {
        return root == null;
    }

    @Override
    public Iterator<BinaryTree<T> > iterator() {
        return new PreOrderIterator(this);
    }

    private class PreOrderIterator implements Iterator<BinaryTree<T> > {

        Stack<BinaryTree<T>> stack = new Stack<BinaryTree<T>>();

        public PreOrderIterator(BinaryTree<T> binaryTree) {
            stack.push(binaryTree);
        }

        @Override
        public boolean hasNext() {
            return !stack.isEmpty();
        }

        @Override
        public BinaryTree<T> next() {
            BinaryTree<T> tree = stack.pop();
            TreeNode<T> node = tree.root;
            if (node.rightTree != null) {
                stack.push(node.rightTree);
            }
            if (node.leftTree != null) {
                stack.push(node.leftTree);
            }
            return tree;
        }
    }
}