如何覆盖list里面的信息

Java code

//Usercenterpublic  class Usercenter {        private String id;//用户名    private String password;//密码    private String email;//邮箱           static List <Object> list = new ArrayList<Object> ();                      //id    public void setId (String id){        this.id=id;    }        public String getId (){        return id;    }        //password    public void setPassword (String password){        this.password=password;    }        public String getPassword (){        return password;    }      //email    public void setEmail (String email){        this.email=email;    }        public String getEmail (){        return email;    }    

Java code

//添加到listUsercenter use2 = new Usercenter();        // 第一次添加        use2.setIdnum(01);// 获得学号        use2.setId("张三");// 姓名                use2.setPassword("1234");//密码                use2.list.add(use2.getIdnum());        use2.list.add(use2.getId());                use1.setPassword("abcd");//密码                // 第二次添加        Usercenter use1 = new Usercenter();        use1.setIdnum(02);// 获得学号        use1.setId("李四");// 姓名                use2.list.add(use2.getPassword);                // 放入list        use1.list.add(use1.getIdnum());        use1.list.add(use1.getId());        use1.list.add(use1.getPassword);

假如要根据学号修改list里面的password或者其他值，应该怎么修改?(我自己想的是:先删除要修改的值，然后在添加，不过貌似行不通。。)

[解决办法]

Java code

package coverlist;import java.util.ArrayList;import java.util.List;/** * @author Yanhua.Chen * @time 2012-8-26 */public class Usercenter {    private String id;//用户名    private String password;//密码    private String email;//邮箱           public static List <Usercenter> list = new ArrayList<Usercenter> ();            public Usercenter(){            }        public Usercenter(String id){        this.id = id;    }          //id    public void setId (String id){        this.id=id;    }        public String getId (){        return id;    }        //password    public void setPassword (String password){        this.password=password;    }        public String getPassword (){        return password;    }      //email    public void setEmail (String email){        this.email=email;    }        public String getEmail (){        return email;    }    @Override    public int hashCode() {        final int prime = 31;        int result = 1;        result = prime * result + ((id == null) ? 0 : id.hashCode());        return result;    }    /*      * 很重要     * 为了int index = list.indexOf(new Usercenter("id"));他正确     */    @Override    public boolean equals(Object obj) {        if (this == obj)            return true;        if (obj == null)            return false;        if (getClass() != obj.getClass())            return false;        Usercenter other = (Usercenter) obj;        if (id == null) {            if (other.id != null)                return false;        } else if (!id.equals(other.id))            return false;        return true;    }        }