Maison >Java >javaDidacticiel >Comment implémenter un système de récupération de livres en Java
Entraînez-vous à implémenter 3 fonctions simples sans optimisation Vous pouvez ajouter les fonctions que vous souhaitez implémenter en fonction de vos besoins.
Book.java
package com.demo3; public class Book { private int id; private String name; private double price; public Book(){} public Book(int id, String name, double price) { this.id = id; this.name = name; this.price = price; } public int getId() { return id; } public void setId(int id) { this.id = id; } public String getName() { return name; } public void setName(String name) { this.name = name; } public double getPrice() { return price; } public void setPrice(double price) { this.price = price; } public void showMess() { System.out.println("Book{" + "编号=" + getId() + ", 书名='" + getName() + ", 价格=" + getPrice() + '}'); } }
Tool.java
package com.demo3; import com.sun.scenario.effect.impl.sw.sse.SSEBlend_SRC_OUTPeer; import java.math.BigDecimal; import java.util.Arrays; public class Tools { private Book[] books = new Book[20]; private int size; public void init(){ Book book1 = new Book(1,"老人与海",29.8); Book book2 = new Book(2,"狂人日记",36.7); Book book3 = new Book(3,"玫瑰的葬礼",19.2); Book book4 = new Book(4,"宇宙源头",19.2); books[0]=book1; books[1]=book2; books[2]=book3; books[3]=book4; size=4; } public Book[] getBooks() { return books; } public void setSize(int size) { this.size = size; } /*根据编号查询图书*/ public void fingBookById(Book[] books,int id){ int i=0; while(i<size){ if(books[i].getId()== id){ System.out.println("检索信息: "); System.out.println("-------------------Content----------------------"); books[i].showMess(); System.out.println("------------------------------------------------"); break; } i++; } if(i>=size){ System.out.println("暂无信息"); } } /*根据价格查找图书,返回一个新的数组*/ public Book[] findBookeByPrice(Book[] books,double price){ Book[] newBooks=new Book[books.length]; int length=0; int i=0; int j=0;/*注意,这里添加一个j*/ while(i<size){ /*提高精度,这里用到了BigDecimal类*/ BigDecimal x1 = new BigDecimal(books[i].getPrice()); BigDecimal x2 = new BigDecimal(price); if(x1.floatValue()==x2.floatValue()){ /*这里用到j,而不是下标i,如果是下标i的话,则就会出现nullpointerexception异常,因为if程序体中的 i的取值不是连续的*/ newBooks[j++]= books[i]; length++; } i++; } /*这里用到了Array集合类中的copyRange静态方法*/ newBooks= Arrays.copyOfRange(newBooks,0,length); return newBooks; } }
BookTest.java
package com.demo3; import java.util.Scanner; public class BookTest { public static void main(String[] args) { Scanner scanner = new Scanner(System.in); /*创建工具类,对其进行初始化*/ Tools tool = new Tools(); tool.init(); prof: while(true) { System.out.println("========图书检索系统======="); System.out.println("1,【编号检索】 2,【价格检索】 3,【退出】"); System.out.print("【输入检索【类型】: "); int num = scanner.nextInt(); while (true) { switch (num) { case 1: System.out.println("进入图书【编号】检索:"); System.out.print("输入检索【编号】: "); int checkId = scanner.nextInt(); tool.fingBookById(tool.getBooks(), checkId);break; case 2: System.out.println("进入图书【价格】检索"); System.out.print("输入检索【价格】:"); double price = scanner.nextDouble(); Book[] books = tool.findBookeByPrice(tool.getBooks(),price); if(books.length>0){ System.out.println("-------------------Content----------------------"); for(Book book :books){ book.showMess(); } System.out.println("------------------------------------------------"); };break; case 3: System.out.println("退出成功"); break prof; }; break; } } } }
Le programme est exécuté comme suit :
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