異常頁(yè)

package?book;

public?class?NoBook?extends?Exception?{
????public?NoBook(){

????}
????public?NoBook(String?message){
????????super(message);
????}
}

主頁(yè)

package?book;

import?java.util.InputMismatchException;
import?java.util.Scanner;
public?class?BookTest?{
????public?static?void?main(String[]?args)?{
????????BookTest?test?=?new?BookTest();
????????test.trys();
????}
????public?void??trys(){
????????try?{
????????????showbooks();
????????}?catch?(InputMismatchException?e)?{
????????????System.out.println("請(qǐng)輸入數(shù)字");
????????????trys();
????????}catch?(NoBook?e){
????????????System.out.println(e);
????????????trys();
????????}
????}
????public?void?showbooks()??throws?NoBook{
????????Scanner?input?=?new?Scanner(System.in);
????????String[]?books?=?{"book1",?"book2",?"book3",?"book4"};
????????for(int?i=0;i<books.length;i++){
????????????System.out.print(i+1+":"+books[i]+"?");
????????}
????????System.out.println();
????????System.out.println("輸入命令：1按照名稱查找圖書?2按照序號(hào)查找圖書");
????????int?num?=?input.nextInt();
????????int?hasbook=0;
????????if?(num?==?1)?{
????????????System.out.println("請(qǐng)輸入圖書名");
????????????String?bookname=input.next();
????????????for(String?value:books){
????????????????if(value.equals(bookname)){
????????????????????hasbook=1;
????????????????}
????????????}
????????????if(hasbook==1){
????????????????System.out.println("書名："?+?bookname);
????????????}else{
????????????????throw?new?NoBook("圖書不存在");
????????????}
????????}?else?if?(num?==?2)?{
????????????System.out.println("請(qǐng)輸入圖書序號(hào)");
????????????int?index?=?input.nextInt();
????????????if(index>books.length){
????????????????throw?new?NoBook("圖書不存在");
????????????}else{
????????????????System.out.println("書名："?+?books[index-1]);
????????????}
????????}?else?{
????????????throw?new?NoBook("輸入錯(cuò)誤，請(qǐng)重新輸入");
????????}

????}
}