凝聚力:Co的意思是在一起，hesion的意思是粘在一起。粘结:不同物质的微粒粘在一起的系统

举个现实的例子: img礼貌

整体大于部分之和-亚里士多德。

Cohesion is an ordinal type of measurement and is usually described as “high cohesion” or “low cohesion”. Modules with high cohesion tend to be preferable, because high cohesion is associated with several desirable traits of software including robustness, reliability, reusability, and understandability. In contrast, low cohesion is associated with undesirable traits such as being difficult to maintain, test, reuse, or even understand. wiki Coupling is usually contrasted with cohesion. Low coupling often correlates with high cohesion, and vice versa. Low coupling is often a sign of a well-structured computer system and a good design, and when combined with high cohesion, supports the general goals of high readability and maintainability. wiki

在面向对象编程语言中，模块内部的高内聚和模块之间的低耦合通常被认为与高质量有关。

例如，每个Java类中的代码必须具有较高的内部内聚性，但要尽可能地与其他Java类中的代码松散耦合。

Meyer的面向对象软件构建(第二版)的第3章对这些问题进行了很好的描述。

内聚性表明了软件元素的职责是如何相互关联和集中的。

耦合指的是软件元素与其他元素的连接强度。

软件元素可以是类、包、组件、子系统或系统。在设计系统时，建议使用具有高内聚性和支持低耦合的软件元素。

低内聚导致整体类难以维护、理解，降低了可重用性。类似地，高耦合导致类紧密耦合，更改往往不是非局部的，难以更改并减少重用。

我们可以假设一个场景，在这个场景中，我们正在设计一个典型的可监视ConnectionPool，并满足以下需求。注意，对于像ConnectionPool这样的简单类来说，它可能看起来太过了，但基本目的只是用一些简单的示例演示低耦合和高内聚，我认为应该会有所帮助。

支持连接 释放连接 获取有关连接与使用计数的统计数据 获取有关连接和时间的统计数据 将连接检索和发布信息存储到数据库中，以便以后报告。

对于低内聚，我们可以通过将所有功能/职责强制填充到单个类中来设计ConnectionPool类，如下所示。我们可以看到，这个类负责连接管理、与数据库交互以及维护连接统计信息。

有了高内聚性，我们可以在类之间分配这些职责，并使其更可维护和可重用。

To demonstrate Low coupling we will continue with the high cohesion ConnectionPool diagram above. If we look at the above diagram although it supports high cohesion, the ConnectionPool is tightly coupled with ConnectionStatistics class and PersistentStore it interacts with them directly. Instead to reduce the coupling we could introduce a ConnectionListener interface and let these two classes implement the interface and let them register with ConnectionPool class. And the ConnectionPool will iterate through these listeners and notify them of connection get and release events and allows less coupling.

Note/Word or Caution: For this simple scenario it may look like an overkill but if we imagine a real-time scenario where our application needs to interact with multiple third party services to complete a transaction: Directly coupling our code with the third party services would mean that any changes in the third party service could result in changes to our code at multiple places, instead we could have Facade that interacts with these multiple services internally and any changes to the services become local to the Facade and enforce low coupling with the third party services.

内聚指的是类(或模块)可以做什么。低内聚意味着这个类会做各种各样的动作——它很宽泛，不关注它应该做什么。高内聚意味着类专注于它应该做的事情，即只有与类的意图相关的方法。

低内聚的例子:

-------------------
| Staff           |
-------------------
| checkEmail()    |
| sendEmail()     |
| emailValidate() |
| PrintLetter()   |
-------------------

高内聚的例子:

----------------------------
| Staff                   |
----------------------------
| -salary                 |
| -emailAddr              |
----------------------------
| setSalary(newSalary)    |
| getSalary()             |
| setEmailAddr(newEmail)  |
| getEmailAddr()          |
----------------------------

至于耦合，它指的是两个类/模块彼此之间的关联或依赖程度。对于低耦合类，改变一个类中的主要内容不应该影响到另一个类。高耦合会使更改和维护代码变得困难;由于类紧密地结合在一起，因此进行更改可能需要对整个系统进行改造。

好的软件设计具有高内聚性和低耦合性。

凝聚力:Co的意思是在一起，hesion的意思是粘在一起。粘结:不同物质的微粒粘在一起的系统

举个现实的例子: img礼貌

整体大于部分之和-亚里士多德。

Cohesion is an ordinal type of measurement and is usually described as “high cohesion” or “low cohesion”. Modules with high cohesion tend to be preferable, because high cohesion is associated with several desirable traits of software including robustness, reliability, reusability, and understandability. In contrast, low cohesion is associated with undesirable traits such as being difficult to maintain, test, reuse, or even understand. wiki Coupling is usually contrasted with cohesion. Low coupling often correlates with high cohesion, and vice versa. Low coupling is often a sign of a well-structured computer system and a good design, and when combined with high cohesion, supports the general goals of high readability and maintainability. wiki

理论的区别

凝聚力

内聚性是模块相对功能强度的表征。 内聚模块执行单一任务，几乎不需要与其他模块交互 程序其他部分的组件。 具有高内聚和低耦合的模块称为功能独立模块 其他模块。

衔接的分类

1.巧合2。逻辑3。时间4。程序5。沟通6。连续7。功能

耦合

耦合表示模块之间的相对依赖关系。 两个模块之间的耦合程度取决于它们的接口复杂性。