Do a breadth first traversal of a tree

import java.util.LinkedList;
 import java.util.Queue;
 import java.util.concurrent.ConcurrentLinkedQueue;class BinaryTree {
 static class Node {
   char data;
   Node left = null;
   Node right = null;
   int i;
  } public static char[] dataArray = new char[] { 'a', 'b', 'c', 'd', 'e', 'f',
    'g', 'h', 'i', 'j', 'k', 'l', 'm', 'n', 'o' }; public static Node creatRoot(Node node) {
   if (node.i < dataArray.length) {
    if (node.data == '-')
     node = null;
    if (node != null)
     node.data = dataArray[node.i];
    node.left = creatLeft(node);
    node.right = creatRight(node);  }
   return node;
  } public static Node creatLeft(Node node) {
   if (node != null) {
    node.left = new Node();
    node.left.i = 2 * node.i + 1;
    creatRoot(node.left);
   }
   return node.left; }
 public static Node creatRight(Node node) {
   if (node != null) {
    node.right = new Node();
    node.right.i = 2 * node.i + 2;
    creatRoot(node.right);
   }
   return node.right;
  } public static void preOrder(Node node) {
   if (node != null) {
    System.out.print(node.data + " ");
    preOrder(node.left);
    preOrder(node.right);
   }
  } public static void inOrder(Node node) {
   if (node != null) {
    inOrder(node.left);
    System.out.print(node.data + " ");
    inOrder(node.right);
   }
  } public static void postOrder(Node node) {
  if (node != null) {
    postOrder(node.left);
    postOrder(node.right);
    System.out.print(node.data + " ");  }
  } public static void breadthFirstTraversal(Node node) {
   Node p=node;
   Queue<Node> queue = new LinkedList<Node>();
   queue.add(node);
   while (!queue.isEmpty()) {
    p = queue.poll();
    System.out.print(p.data + " ");
    if (p.left != null) {
     queue.add(p.left);}
    if (p.right != null) {  //不能是else if
     queue.add(p.right);
    }
    
   }
  } public static void main(String args[]) {
   Node node = new Node();  node = creatRoot(node);
  preOrder(node);
   System.out.println();
   inOrder(node);
   System.out.println();
   postOrder(node);
   System.out.println();
   System.out.print(depth(node) - 1);
   System.out.println();
   breadthFirstTraversal(node);
  } public static int depth(Node node) {
   int lDepth, rDepth;
   if (node == null) {
    return 0;
   }
   lDepth = depth(node.left);
   rDepth = depth(node.right);
   return (lDepth > rDepth ? lDepth : rDepth) + 1;
  }}