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public class BinTreeDiskSample { private static int h = -1; private static Node root; static class Node implements Serializable { private static final long serialVersionUID = -4780741633734920991L; int data; transient Node left; transient Node right; int lHeight = -1, rHeight = -1; public Node(int data) { this.data = data; } public Node setLeft(Node left) { this.left = left; return this; } public Node setRight(Node right) { this.right = right; return this; } public Node getLeft() { return left; } public Node getRight() { return right; } // 后续遍历写入，先序遍历读出 public int write(ObjectOutputStream out) throws IOException { if (left != null) { lHeight = left.write(out); } if (right != null) { rHeight = right.write(out); } h++; out.writeObject(this); return h; } private void init(List<Node> list) { if (lHeight != -1) { left = list.get(lHeight); left.init(list); } if (rHeight != -1) { right = list.get(rHeight); right.init(list); } }
 } public static void binTreePreOrderPrint(Node root) { System.out.print(root.data + " "); // visit root if(root.left != null) { binTreePreOrderPrint(root.left); } if(root.right != null) { binTreePreOrderPrint(root.right); } } // 先序遍历读出 public static void read(ObjectInputStream in) throws IOException, ClassNotFoundException { List<Node> list = new ArrayList<Node>(); Node n; Object obj; try { while ((obj = in.readObject()) != null) { n = (Node) obj; list.add(n); } } catch (Exception e) { // EOFException ...// e.printStackTrace(); } root = list.get(list.size() - 1); root.init(list); } public static void main(String args[]) throws FileNotFoundException, IOException, ClassNotFoundException { // 构造一棵二叉树 11 21 41 61 51 31 Node n6 = new Node(61); Node n4 = new Node(41).setLeft(n6); Node n5 = new Node(51); Node n2 = new Node(21).setLeft(n4).setRight(n5); Node n3 = new Node(31); Node n1 = new Node(11).setLeft(n2).setRight(n3); root = n1; System.out.println("output node: "); binTreePreOrderPrint(root); // 将数据写稿磁盘 ObjectOutputStream out = new ObjectOutputStream(new FileOutputStream("btree.bin")); root.write(out); out.close();
 root = null; // 将数据从磁盘读入，并进行数据结构的重新构建 ObjectInputStream in = new ObjectInputStream(new FileInputStream("btree.bin")); read(in); in.close(); System.out.println("\nread node: "); binTreePreOrderPrint(root); }
}