package Exception;
import java.util.*;
public class bookmanager {
    static Books[] book={new Books(1,"数据结构"),new Books(2,"论语")};//静态数组
    public static void main(String[] args) {
        bookmanager bkm = new bookmanager();
        bkm.mainsystem();//调用mainsystem
    }

    public void mainsystem(){
        try{
            book();
        }catch(BookException e){
            System.out.println(e.getMessage());
            mainsystem();//如果输入异常，在此调用mainsystem
        }
    }

    public void book() throws BookException{
        Scanner in = new Scanner(System.in);
        System.out.println("Input Command:1-Base oon name for book;2-Base on number for Book");
        try{    
            int num=in.nextInt();
            while(num>book.length || num 上面for循环是见解某位幕友的代码,在此感谢!

    }
}

package Exception;
//数组
public class Books {
    int num;
    String name;
    public Books(int num,String name){
        this.num=num;
        this.name=name;
    }
    public void setName(String name){
        this.name=name;
    }
    public String getName(){
        return name;
    }
    public void setNum(int num){
        this.num=num;
    }
    public int getNum(){
        return num;
    }
}

package Exception;
//自定义异常
@SuppressWarnings("serial")
public class BookException extends Exception{
    public BookException(String message){
        super(message);
    }
}