java 传递过程中出现的问题解决方法

* 测试conn关闭情况
*/

package com.hb.test;

import java.sql.connection;

/**
*
* @author icecold
*/
public class testconn {
static connection conn = null;

    public static void main(string[] args)throws exception {
        conn = db.getconnection();
        db.closeconnection(conn);
        db.setconnection(conn);
        if(conn == null){
            system.out.println("aaa");
        }else {
            system.out.println("bbb");
        }
    }

}

数据类

*
* 数据库教程操作类
*/

package com.hb.test;

import java.sql.connection;
import java.sql.drivermanager;

/**
*
* @author icecold
*/
public class db {

public static void closeconnection(connection conn){
        try{
            if(conn != null){
                conn.close();
                conn = null;
//                if(conn .isclosed()){
//                    system.out.println("null");
//                }else {
//                    system.out.println("not null");
//                }
            }
           // conn = null;
        }catch(exception e){
            e.printstacktrace();
        }
    }
    public static connection getconnection()throws exception {
        connection conn = null;
        class.forname("com.mysql教程.jdbc.driver");
        conn = drivermanager.getconnection("jdbc:mysql://localhost:3306/test?user","root","123456");
        return conn;
    }
    public static void setconnection(connection conn){
        conn = null;
    }
}

补充：Jsp教程,Java基础