數據庫例子
----------------------------------------------------------------------------------------------------------------------------------------------------------------------
create database bbs;
use bbs;
create table article
(
id int primary key auto_increment,
pid int,
rootid int,
title varchar(255),
cont text,
pdate datetime,
isleaf int
);
insert into article values (null, 0, 1, '螞蟻大戰大象', '螞蟻大戰大象', now(), 1);
insert into article values (null, 1, 1, '大象被打趴下了', '大象被打趴下了',now(), 1);
insert into article values (null, 2, 1, '螞蟻也不好過','螞蟻也不好過', now(), 0);
insert into article values (null, 2, 1, '瞎說', '瞎說', now(), 1);
insert into article values (null, 4, 1, '沒有瞎說', '沒有瞎說', now(), 0);
insert into article values (null, 1, 1, '怎么可能', '怎么可能', now(), 1);
insert into article values (null, 6, 1, '怎么沒有可能', '怎么沒有可能', now(), 0);
insert into article values (null, 6, 1, '可能性是很大的', '可能性是很大的', now(), 0);
insert into article values (null, 2, 1, '大象進醫院了', '大象進醫院了', now(), 1);
insert into article values (null, 9, 1, '護士是螞蟻', '護士是螞蟻', now(), 0);
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下面是用遞歸列出樹狀結構：
import java.sql.*;
public class ArticleTree 
{
public static void main(String[] args) {
ArticleTree at = new ArticleTree();
at.show();
}
public void show(){
Connection conn = null;
Statement stmt = null;
ResultSet rs = null;
try{
Class.forName("com.mysql.jdbc.Driver");
conn = DriverManager.getConnection("jdbc:mysql://localhost/bbs?user=root&password=********");
stmt = conn.createStatement();
rs = stmt.executeQuery("select * from article where pid = 0");
while (rs.next()){
System.out.println(rs.getString("cont"));
tree(conn, rs.getInt("id"),1);
}
}catch(SQLException e){
e.printStackTrace();
}catch(ClassNotFoundException e){
e.printStackTrace();
}finally{
try{
if (rs!=null){
rs.close();
rs = null;
}
if (stmt!=null){
stmt.close();
stmt = null;
}
if (conn!=null){
conn.close();
conn = null;
}
}catch(SQLException e){
e.printStackTrace();
}
}
}
private void tree(Connection conn,int id, int level){
Statement stmt = null;
ResultSet rs = null;
StringBuffer strPre = new StringBuffer("");
for(int i = 0; i < level ; i++){
strPre.append(" ");
}
try{
stmt = conn.createStatement();
String sql = "select * from article where pid =" + id;
rs = stmt.executeQuery(sql);
while(rs.next()){
System.out.println(strPre + rs.getString("cont"));
if(rs.getInt("isleaf")!=0){
tree(conn , rs.getInt("id") , level+1);
}
}
}catch(SQLException e){
e.printStackTrace();
}finally{
try{
if (rs!=null){
rs.close();
rs = null;
}
if (stmt!=null){
stmt.close();
stmt = null;
}
}catch(SQLException e){
e.printStackTrace();
}
}
}
}
輸出結果：
--------------------------------------------------------------------------
螞蟻大戰大象
大象被打趴下了
螞蟻也不好過
瞎說
沒有瞎說
大象進醫院了
護士是螞蟻
怎么可能
怎么沒有可能
可能性是很大的
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復習以下遞歸，這個東西如果不熟練，自己寫起來是很麻煩的事情。腦子里老轉不過彎。
posted on 2009-04-06 01:42
shivaree 閱讀(508)
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