Introduction to Binary Trees - Advanced Topics in Java: Core Concepts in Data Structures - page 244

public static TreeNode buildTree(Scanner in) {
String str = in.next();
if (str.equals("@")) return null;
TreeNode p = new TreeNode(new NodeData(str));
p.left = buildTree(in);
p.right = buildTree(in);
return p;
} //end buildTree
public void levelOrderTraversal() {
Queue Q = new Queue();
Q.enqueue(new QueueData(root));
while (!Q.empty()) {
QueueData temp = Q.dequeue();
temp.node.data.visit();
if (temp.node.left != null) Q.enqueue(new QueueData(temp.node.left));
if (temp.node.right != null) Q.enqueue(new QueueData(temp.node.right));
}
} //end levelOrderTraversal
} //end class BinaryTree
class QueueData {
TreeNode node;
public QueueData(TreeNode n) {
node = n;
}
} //end class QueueData
class QNode {
QueueData data;
QNode next;
public QNode(QueueData d) {
data = d;
next = null;
}
} //end class QNode
class Queue {
QNode head = null, tail = null;
public boolean empty() {
return head == null;
}
public void enqueue(QueueData nd) {
QNode p = new QNode(nd);
if (this.empty()) {
head = p;
tail = p;
}