Class Test
{
    public static User user=null;
      Public synchronized void add(User u)
{
     user=u;
     Dao.save(user)
}
}

Test test=new Test();
User u=new User();
u.setUserName(“liaomin”);
u.setUserPassword(“liaomin”);
Test.add(u);

Test tes1t=new Test();
User u1=new User();
u1.setUserName(“huqun”);
u1.setUserPassword(“huqun”);
Tes1t.add(u1);

Public static synchronized void add(User u)
{
     user=u;
     Dao.save(user)
}

Class Test
{
public static User user=null;
Lock lock=new ReentrantLock();

      Public void add(User u)
{
lock.lock();
     user=u;
     Dao.save(user);
lock.unlock();
}
}

Public static synchronized void add(User u)
{
     user=u;
     Dao.save(user)
}