19.
Introduction to C# 2.0
458
19.
Introduction to C# 2.0
users of generics in Eiffel or Ada or to users of C++ templates; however, they do not suffer
many of the complications of the latter.
19.1.1
Why Generics?
Without generics, general-purpose data structures can use type
object
to store data of
any type. For example, the following simple
Stack
class stores its data in an
object
array, and its two methods,
Push
and
Pop
, use
object
to accept and return data,
respectively.
public class Stack
{
object[] items;
int count;
public void Push(object item) {...}
public object Pop() {...}
}
Although using type
object
makes the
Stack
class flexible, it is not without drawbacks.
For example, it is possible to push a value of any type, such as a
Customer
instance, onto a
stack. However, when a value is retrieved, the result of the
Pop
method must explicitly be
cast back to the appropriate type, which is tedious to write and carries a performance pen-
alty for runtime type checking.
Stack stack = new Stack();
stack.Push(new Customer());
Customer c = (Customer)stack.Pop();
If a value of a value type, such as an
int
, is passed to the
Push
method, it is automatically
boxed. When the
int
is later retrieved, it must be unboxed with an explicit type cast.
Stack stack = new Stack();
stack.Push(3);
int i = (int)stack.Pop();
Such boxing and unboxing operations add performance overhead because they involve
dynamic memory allocations and runtime type checks.
A further issue with the
Stack
class is that it is not possible to enforce the kind of data
placed on a stack. Indeed, a
Customer
instance can be pushed on a stack and then acci-
dentally cast to the wrong type after it is retrieved.
Stack stack = new Stack();
stack.Push(new Customer());
string s = (string)stack.Pop();
Hejlsberg.book Page 458 Friday, October 10, 2003 7:35 PM
剩余17页未读，继续阅读
CherryPeng
- 粉丝: 2
- 资源: 1
我的内容管理
展开
最新资源
- Hadoop生态系统与MapReduce详解
- MDS系列三相整流桥模块技术规格与特性
- MFC编程：指针与句柄获取全面解析
- LM06：多模4G高速数据模块，支持GSM至TD-LTE
- 使用Gradle与Nexus构建私有仓库
- JAVA编程规范指南：命名规则与文件样式
- EMC VNX5500 存储系统日常维护指南
- 大数据驱动的互联网用户体验深度管理策略
- 改进型Booth算法：32位浮点阵列乘法器的高速设计与算法比较
- H3CNE网络认证重点知识整理
- Linux环境下MongoDB的详细安装教程
- 压缩文法的等价变换与多余规则删除
- BRMS入门指南：JBOSS安装与基础操作详解
- Win7环境下Android开发环境配置全攻略
- SHT10 C语言程序与LCD1602显示实例及精度校准
- 反垃圾邮件技术：现状与前景
资源上传下载、课程学习等过程中有任何疑问或建议，欢迎提出宝贵意见哦~我们会及时处理！
点击此处反馈
