抽象:只显示必要的信息。让我们关注一下在计算机上进行开关的例子。当系统仍在加载时，用户不必知道发生了什么(该信息对用户隐藏)。

让我们再举一个例子，ATM机。客户不需要知道机器如何读取密码并处理交易，他所需要做的就是输入密码，拿现金然后离开。

封装:处理隐藏类的敏感数据，从而私有化类的一部分。这是一种通过不允许外部访问来保持某些信息对其客户端的私密性的方法。

一种防止特定对象的数据被外部函数故意或意外误用的机制叫做“数据封装”。

在不包括背景细节或解释的情况下表现基本特征的行为被称为抽象

另一个例子:

假设我创建了一个不可变的Rectangle类，如下所示:

class Rectangle {
 public:
  Rectangle(int width, int height) : width_(width), height_(height) {}
  int width() const { return width_; }
  int height() const { return height_; }

 private:
  int width_;
  int height_;
}

现在很明显，我已经封装了宽度和高度(访问受到某种限制)，但我没有抽象任何东西(好吧，也许我忽略了矩形在坐标空间中的位置，但这是示例的缺陷)。

好的抽象通常意味着好的封装。

一个好的抽象例子是通用数据库连接类。它的公共接口与数据库无关，非常简单，但允许我对连接做我想做的事情。你看到了吗?这里还有封装，因为类内部必须有所有低级句柄和调用。

抽象或封装并不严格要求信息隐藏。信息可能会被忽略，但不一定要隐藏。

封装是一种将事物视为单一事物的能力，即使它可能由许多复杂的部分或思想组成。例如，我可以说我坐在一把“椅子”上，而不是指这把椅子上的许多不同部分，每个部分都有特定的设计和功能，它们精确地组合在一起，目的是让我的屁股舒适地离地板几英尺远。

Abstraction is enabled by encapsulation. Because we encapsulate objects, we can think about them as things which relate to each other in some way rather than getting bogged down in the subtle details of internal object structure. Abstraction is the ability to consider the bigger picture, removed from concern over little details. The root of the word is abstract as in the summary that appears at the top of a scholarly paper, not abstract as in a class which can only be instantiated as a derived subclass.

I can honestly say that when I plop my butt down in my chair, I never think about how the structure of that chair will catch and hold my weight. It's a decent enough chair that I don't have to worry about those details. So I can turn my attention toward my computer. And again, I don't think about the component parts of my computer. I'm just looking at a part of a webpage that represents a text area that I can type in, and I'm communicating in words, barely even thinking about how my fingers always find the right letters so quickly on the keyboard, and how the connection is ultimately made between tapping these keys and posting to this forum. This is the great power of abstraction. Because the lower levels of the system can be trusted to work with consistency and precision, we have attention to spare for greater work.

抽象和封装过程都会生成接口。

通过封装生成的接口隐藏了实现细节。

与抽象之前相比，通过抽象生成的接口可以适用于更多的数据类型。

我认为封装是实现抽象的一种方式。看看下面的链接。

抽象和封装