JSP---网上商城->单例模式

 1 public class CustomerMgr {
 2     private static CustomerMgr mgr = null;//声明一个静态的该类的对象
 3 
 4     private CustomerMgr() {//私有的构造方法,只能在类的内部构造对象
 5     }
 6 
 7     public static CustomerMgr getInstance() {
 8         if (mgr == null) {
 9             mgr = new CustomerMgr();
10         }
11         return mgr;
12     }
13 
14     public boolean add(Customer customer) {