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自定义异常类:

package com.Bookrent;

public class ExtraException extends Exception{

}

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Bookrent类:

package com.Bookrent;

public class Book {

private String bookName;

private int bookNum;

public Book(String bookName,int bookNum)

{

this.bookName = bookName;

this.bookNum = bookNum;

}

public String getBookName() {

return bookName;

}

public void setBookName(String bookName) {

this.bookName = bookName;

}

public int getBookNum() {

return bookNum;

}

public void setBookNum(int bookNum) {

this.bookNum = bookNum;

}

}

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主函数：

package com.Bookrent;

import java.util.Scanner;

public class bookrent {

Book[] bookRent = 

{new Book("高数",1),new Book("数据结构",2),new Book("操作系统",3),new Book("数据库",4)}; 

//将数组定义到全局范围方便其他函数使用;

public static void main(String[] args) {

// TODO Auto-generated method stub

bookrent br = new bookrent();

br.find();

}

public void find()

{

Scanner input = new Scanner(System.in);

System.out.println("输入命令：1.按照名称查找图书；2.按照序号查找图书");

int i = input.nextInt();

try

{

if(i == 1)

{

this.searchName();

}

else if(i == 2)

{

this.searchNum();

}

else 

{

throw  new Exception();

}

}catch(Exception e)

{

input = new Scanner(System.in);//对于输入有误的情况不会终止程序运行;

System.out.println("命令输入错误！请根据提示输入正确的命令！");

this.find();

}

}

public void searchName()//对于输入的信息进行判断并进行有效的处理（try catch）异常处理并循环

{

System.out.println("请输入要查询的书名：");

Scanner input = new Scanner(System.in);

String s = input.next();

try

{

for(Book br:bookRent)//遍历数组

{

if(br.getBookName().equals(s))//查看是否有何输入相同的书名

{

System.out.println("已找到图书");

System.out.println("图书:" + s);

this.find();//遍历后要及时退出否则会强制抛出异常;

}

else

{

throw new Exception();

}

}

}catch(Exception e)

{

System.out.println("查找的图书不存在");

this.find();

}

}

public void searchNum()

{

System.out.println("请输入要查询的书的序号：");

Scanner input = new Scanner(System.in);

try

{

int i = input.nextInt();

for(Book br:bookRent)

{

if(br.getBookNum() == i)

{

System.out.println("已找到图书");

System.out.println("图书:" + i);

this.find();

}

else

{

throw new ExtraException();//自定义异常的使用;对于多catch很有帮助;

}

}

}catch(ExtraException e)

{

System.out.println("查找的图书不存在");

this.find();

}catch(Exception e)

{

System.out.println("命令输入有误，请重新输入！");

this.searchNum();

}

}

}