記憶體中的二叉樹怎麼儲存在硬碟上？當用的時候再還原出原來的樹形結構？

可以衍生一下，在建立動態索引的時候，索引一般使用的是樹形結構，此時的樹要怎麼儲存？想必此問題多數人都遇到過，並且困擾了不少時間。

下面就二叉樹的實現為例說明這個儲存過程，當然可以衍生為B+樹都樹形結構。

import java.io.FileInputStream; import java.io.FileNotFoundException; import java.io.FileOutputStream; import java.io.IOException; import java.io.ObjectInputStream; import java.io.ObjectOutputStream; import java.io.Serializable; import java.util.ArrayList; import java.util.List; public class IndexTree { static private int Sn = -1; static private Node root; static private class Node implements Serializable { int data; transient Node left; transient Node right; int l = -1, r = -1; public Node(int data, Node l, Node r) { this.data = data; this.left = l; this.right = r; } public int write(ObjectOutputStream out) throws IOException { if (left != null) l = left.write(out); if (right != null) r = right.write(out); Sn++; out.writeObject(this); return Sn; } private void init(List<Node> list) { if (l != -1) { left = list.get(l); left.init(list); } if (r != -1) { right = list.get(r); right.init(list); } } public String toString() { StringBuilder sb = new StringBuilder(); sb.append(data + " "); if (left != null) sb.append(left); if (right != null) sb.append(right); return sb.toString(); } } static public void read(ObjectInputStream in) throws IOException, ClassNotFoundException { List<Node> list = new ArrayList<Node>(); Node n; try { while (((n = (Node) in.readObject()) != null)) { list.add(n); } } catch (Exception e) { e.printStackTrace(); } root = list.get(list.size() - 1); root.init(list); } public static void main(String args[]) throws FileNotFoundException, IOException, ClassNotFoundException { // 構造一棵二叉樹 /* * 1 2 3 4 5 6 */ Node n6 = new Node(6, null, null); Node n4 = new Node(4, n6, null); Node n5 = new Node(5, null, null); Node n2 = new Node(2, n4, n5); Node n3 = new Node(3, null, null); Node n1 = new Node(1, n2, n3); root = n1; System.out.println(root); ObjectOutputStream out = new ObjectOutputStream(new FileOutputStream( "abc.ser")); root.write(out); out.close(); ObjectInputStream in = new ObjectInputStream(new FileInputStream( "abc.ser")); read(in); in.close(); System.out.println(root); } }