public class Test {
    public static void main(String[] args) {
        List<User> userList=new ArrayList<User>();
        while(true) {
            userList.add(new User());
        }
    }
}

public class User implements Serializable {

    /**
     * 
     */
    private static final long serialVersionUID = 1L;

    private Integer id;
    private String userName;
    private String pwd;
//省略getset方法
｝