基本描述

需求變更：
假設(shè)書店原有4大名著，現(xiàn)在按照9折銷售圖書，請打印輸出打折前后的圖書信息。

遵照“開閉原則”中對修改關(guān)閉的原則，不能直接修改IBook接口和NovelBook 類，而是通過增加一個子類OffNovelBook來完成 。

代碼實(shí)現(xiàn)

項(xiàng)目結(jié)構(gòu)

運(yùn)行截圖

代碼

/* 書的接口 */public interface IBook{public String getName();public double getPrice();public String getAuthor();} /*** 一個書的實(shí)現(xiàn)類（小說）*/ public class NovelBook implements IBook{private String name;private Double price;private String author;public NovelBook(String name,double price,String author){this.name = name;this.price = price;this.author = author;}public String getName(){return this.name;} public double getPrice(){return this.price;}public String getAuthor() {return this.author;}} /*** 重寫里面的getPrice方法*/ public class OffNovelBook extends NovelBook{private double price;public OffNovelBook(String name,Double price,String author){super(name,price,author);this.price = price;}//覆寫價(jià)格方法，當(dāng)價(jià)格大于40，就打8析，其他價(jià)格就打95析public double getPrice(){if(this.price > 50){return this.price * 0.85;}else{return this.price * 0.95;}}} public class Main {public static void main(String[] args){IBook novel1 = new NovelBook("西游記",30,"吳承恩");IBook novel2 = new NovelBook("紅樓夢",40,"曹雪芹");IBook novel3 = new NovelBook("三國演義",50,"羅貫中");IBook novel4 = new NovelBook("水滸傳",60,"施耐庵");System.out.println("書籍名字："+novel1.getName()+"書籍作者："+novel1.getAuthor()+"書籍價(jià)格："+novel1.getPrice());System.out.println("書籍名字："+novel2.getName()+"書籍作者："+novel2.getAuthor()+"書籍價(jià)格："+novel2.getPrice());System.out.println("書籍名字："+novel3.getName()+"書籍作者："+novel3.getAuthor()+"書籍價(jià)格："+novel3.getPrice());System.out.println("書籍名字："+novel4.getName()+"書籍作者："+novel4.getAuthor()+"書籍價(jià)格："+novel4.getPrice());System.out.println("---------以下為打折后----------");OffNovelBook offNovelBook1 = new OffNovelBook("西游記",30.0,"吳承恩");OffNovelBook offNovelBook2 = new OffNovelBook("紅樓夢",40.0,"曹雪芹");OffNovelBook offNovelBook3 = new OffNovelBook("三國演義",50.0,"羅貫中");OffNovelBook offNovelBook4 = new OffNovelBook("水滸傳",60.0,"施耐庵");System.out.println("書籍名字："+offNovelBook1.getName()+"書籍作者："+offNovelBook1.getAuthor()+"書籍價(jià)格："+offNovelBook1.getPrice());System.out.println("書籍名字："+offNovelBook2.getName()+"書籍作者："+offNovelBook2.getAuthor()+"書籍價(jià)格："+offNovelBook2.getPrice());System.out.println("書籍名字："+offNovelBook3.getName()+"書籍作者："+offNovelBook3.getAuthor()+"書籍價(jià)格："+offNovelBook3.getPrice());System.out.println("書籍名字："+offNovelBook4.getName()+"書籍作者："+offNovelBook4.getAuthor()+"書籍價(jià)格："+offNovelBook4.getPrice());} }

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