程序设计的基本原则（Basic principles of programming）.docVIP

程序设计的基本原则（Basic principles of programming） The basic principles of programming, data collection, 2008-12-31, 11:29:08, reading 11, review 0: big, small, medium and small 1, the open and close principle The principle was put forward by Bertrand Meyer. The original text is: Software, entities, should, be, open, for, extension, but, closed, for, modification. That is, the module should be extended to open and closed for modification. Modules should be extended as far as possible without modifying the original code, which is the original code. So how to expand? We look at the factory model factory pattern: suppose there is a boy who sells pirated disks and rushes in Zhongguancun, and we design a CD-ROM sales management software for him. We should design an optical disk interface first. As shown: [pre]______________ || | CD | |_____________| |+ (sell) | | | |_____________|[/pre] Pirated disks and rushes are their subcategories. The kid manages the CDs by DiscFactory. Code for: Public class DiscFactory{ Public static CD getDisc (java/lang/String.java.html, target=, _blank, String, name) { Return (CD), java/lang/Class.java.html, target=, _blank, Class.forName (name),.GetInstance (); } } Some people want to buy pirated disk, how to achieve it? Public class kid { Public, static, void, main (java/lang/String.java.html, target=, _blank, String[], args) { CD d=DiscFactory.getDisc (pirated disk); Cds; } } If one day, the boy found his conscience and began selling genuine software. Thats OK. We just need to create another disk subclass, licensed software. There is no need to modify the original structure and code. What about? For extended development, close to modification. Open close principle Factory model is to expand the specific products, and some projects may need more expansion, and to expand the factory, that is abstract factory model. 2, the Richter scale substitution principle The Richter substitution principle was proposed by Barbara Liskov. If the call is a parent cla