数据库并发问题？？？？？？？？？？

[hwwbrant]

public class MyTestDemo {

public static void main(String[] args) {
Thread a = new ThreadDemo1("a");
Thread b = new ThreadDemo1("b");
Thread c = new ThreadDemo1("c");
}

}

class ThreadDemo1 extends Thread{
int i;
String str;
String conn = "localhost/test";
DBAccess db = new DBAccess(conn,"root","123456");

public void run(){
for(int n=0;n<100;n++){
try{
String sql = "select count(*) from joysen_test";
ResultSet rs = db.queryData(sql);
if(rs.next()){
i=rs.getInt(1);
i++;
String query = "insert into joysen_test (test) values ('"+i+"')";
System.out.print(str+":::");
System.out.println(query);
db.insertData(query);
}
}
catch(SQLException e){
System.out.println(e);
}
}


}

public ThreadDemo1(String str) {
this.str = str;
start();
}

}

这是用线程对mysql进行数据插入的代码，但在插入的时候它会报错。有哪位高手能指教一下啊，帮我解决对数据库并发问题，非常感谢！在线等待，急急急急急急急急急急急！！！！！

[sishisui]

虽然我也不知道,但是帮你顶一下!