图书

public class B {
    private String name;
    private int num;
    public B(String n,int nu){
        this.name = n;
        this.num = nu;
    }
    public String getName() {
        return name;
    }
    public void setName(String name) {
        this.name = name;
    }
    public int getNum() {
        return num;
    }
    public void setNum(int num) {
        this.num = num;
    }

}

自定义异常

public class EnException extends Exception{

    public EnException(){

    }
    public EnException(String massage){
        super(massage);     
    }
}

运行

import java.util.Scanner;

public class Book {

    public static void main(String[] args) {
        // TODO Auto-generated method stub

        B book[] = {new B("程序设计基础",1),new B("高数",2),new B("数据结构",3)};
        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");
            Scanner in = new Scanner(System.in);
            try{
            int n = in.nextInt();
            if(n==1){
                System.out.println("输入图书名称:");
                String name = in.next();
                boolean f=false;
                for(int i = 0; i < book.length; i++){
                    if(name.equals(book[i].getName())){
                        f = true;
                        System.out.println("book:"+ book[i].getName());
                    }
                }if(!f){
                    warn();
                }
            }
            else if(n==2){
                System.out.println("输入图书序号：");
                int num = in.nextInt();
                boolean f=false;
                for(int i=0;i<book.length;i++)
                    if(num==book[i].getNum())
                    {
                        System.out.println("book:"+book[i].getName());
                        f=true;
                    }
                if(!f){
                    warn();
                }
            }
            else {
                System.out.println("命令输入错误！请根据提示输入数字命令！");
            }

        }catch(EnException e){
            System.out.println("图书不存在！");           
        }catch(Exception e){
            System.out.println("命令输入错误！请根据提示输入数字命令！");
        }
       }
    }
    public static void warn()throws EnException{
        throw new EnException("图书不存在！");
    }

}