package com.imooc;

import java.util.Scanner;

public class test1 {

private static Scanner console=new Scanner(System.in);

public static void main(String[] args) {

// TODO Auto-generated method stub

String[] books = { "C语言", "数据结构", "汇编语言", "高数", "大学语文", "毛概" };   

    while(true){

    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");

    String book;

    try{

    int command=inputCommand();

    switch(command){

    case 1:

    book=getBookByName(books);

    System.out.println("book"+book);

    break;

    case 2:

    book=getBookByNumber(books);

    System.out.println("book"+book);

    break;

    case -1:

       System.out.println("命令输入错误！请根据提示输入数字命令！");

       continue;

    default:

    System.out.println("命令输入错误！");

    continue;

    }

    break;

    }catch(Exception bne){

    System.out.println(bne.getMessage());

    }

    }

}

    private static String getBookByName(String[] books) throws Exception{

       System.out.println("输入图书名称：");

  String name=console.next();

   for(int i=0;i<books.length;i++){

    if(name.equals(books[i]))

    return books[i];

   }   

throw new Exception("图书不存在！");

}

private static String getBookByNumber(String[] books) throws Exception{

while(true){

System.out.println("输入图书序号：");

try{

int index=inputCommand();

if(index==-1){

System.out.println("命令输入错误！请根据提示输入数字命令！");

continue;

}

String book=books[index];

return book;

}catch(ArrayIndexOutOfBoundsException e){

Exception bookNotExists=new Exception("图书不存在！");

bookNotExists.initCause(e);

throw bookNotExists;

}

}

}

    private static int inputCommand(){

int command;

try{

command=console.nextInt();

return command;

}catch(Exception e){

console=new Scanner(System.in);

return -1;

}

 }

}

请问为什么这里面都会用到try   catch ，只有我加的下划线方法没有try catch？