深入理解C++对象模型:揭秘面向对象编程的底层机制

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"《Inside the C++ Object Model》是由Stanley Lippman撰写的一本深入解析C++对象模型的专业书籍,由Addison Wesley出版社于1996年5月出版,ISBN号为0-201-83454-5,共304页。本书主要探讨了C++中支持面向对象编程的关键机制,包括构造函数语义、临时对象生成、封装、继承以及虚函数和虚继承等核心概念。通过理解这些底层实现模型,读者可以更高效且自信地编写代码,并消除关于C++开销和复杂性的误解。Lippman揭示了隐藏的成本和权衡,并解释了各种实现模型的演变过程,以及为何它们会成为现在这样。他还探讨了C++对象模型的语义含义以及这些模型如何影响你的程序设计。" 在《Inside the C++ Object Model》一书中,作者深入浅出地探讨了以下关键知识点: 1. **构造函数语义**:C++中的构造函数是创建对象时自动调用的特殊成员函数,用于初始化对象的状态。Lippman可能详细讲解了构造函数的调用顺序、构造函数的重载、构造函数的成员初始化列表以及构造函数模板等。 2. **临时对象生成**:在C++中,临时对象是在表达式中创建的对象,通常用于完成类型转换或函数调用。这部分可能涉及了临时对象的生命周期、复制构造函数和移动构造函数在临时对象中的作用,以及RVO(Return Value Optimization)和NRVO(Named Return Value Optimization)等优化技术。 3. **封装**:封装是面向对象编程的核心原则之一,它将数据和操作数据的方法封装在一起。Lippman可能会讨论访问控制(public, private, protected)、友元函数和类的封装策略。 4. **继承**:C++支持单继承和多继承,允许类之间形成层次结构。书中可能详细分析了继承的特性,如继承的可见性、覆盖(override)和隐藏(hiding)、虚基类以及菱形继承问题的解决方案。 5. **虚函数和虚继承**:虚函数使得动态绑定成为可能,增强了多态性。Lippman可能详细讨论了虚函数表(vtable)、虚析构函数的重要性以及纯虚函数和抽象类的用途。同时,虚继承解决了多重继承下的“钻石问题”。 6. **C++对象模型的影响**:作者阐述了C++对象模型如何影响代码的性能和可维护性,包括内存管理、对象布局、编译器优化等方面,并揭示了一些潜在的成本和权衡。 7. **实现模型的演变和未来**:Lippman可能介绍了C++对象模型的历史演变,预测了未来可能的发展趋势,以及为什么当前的设计是这样的。 《Inside the C++ Object Model》是一本深度解析C++底层机制的权威著作,对于希望提升C++编程技能、理解其内部工作原理的开发者来说,是一份宝贵的学习资料。

帮我写出以下java代码:Add a class Bubble that extends Shape. The Bubble class has an instance variable called radius of type double that represents the radius of the bubble. The constructor of the Bubble class takes an x and a y as arguments, which represent the position of the new bubble. The radius of a new bubble is always 10 and never changes after that. The isVisible method indicates whether the bubble is currently visible inside a window of width w and height h (position (0, 0) is in the upper-left corner of the window). The bubble is considered visible if at least one pixel of the bubble is visible. Therefore a bubble might be visible even when its center is outside the window, as long as the edge of the bubble is still visible inside the window. The code of the isVisible method is a little bit complex, mostly because of the case where the center of the circle is just outside one of the corners of the window. So here is the code of the isVisible method, which you can directly copy-paste into your assignment: // Find the point (wx, wy) inside the window which is closest to the // center (x, y) of the circle. In other words, find the wx in the // interval [0, w - 1] which is closest to x, and find the wy in the // interval [0, h - 1] which is closest to y. // If the distance between (wx, wy) and (x, y) is less than the radius // of the circle (using Pythagoras's theorem) then at least part of // the circle is visible in the window. // Note: if the center of the circle is inside the window, then (wx, wy) // is the same as (x, y), and the distance is 0. public boolean isVisible(int w, int h) { double x = getX(); double y = getY(); double wx = (x < 0 ? 0 : (x > w - 1 ? w - 1 : x)); double wy = (y < 0 ? 0 : (y > h - 1 ? h - 1 : y)); double dx = wx - x; double dy = wy - y; return dx * dx + dy * dy <= radius * radius; } The isIn method indicates whether the point at coordinates (x, y) (which are the arguments of the method) is currently inside the bubble or not. The edge of the bubble counts as being inside of the bubble. HINT: use Pythagoras's theorem to compute the distance from the center of the bubble to the point (x, y). The draw method uses the graphics object g to draw the bubble. HINT: remember that the color of the graphics object g is changed in the draw method of the superclass of Bubble. Also add a testBubble method to test all your methods (including inherited methods, but excluding the isVisible method, which I provide, and excluding the draw method since it requires as argument a graphics object g that you

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