百思不得其解,当图书名称输入错误时不能重新执行bookName()方法

package librarySystem;
import java.util.*;
public class LibrarySystem {
    //自定义NoBookException异常类
    public static class NoBookException extends Exception{
        public NoBookException(){}
        public NoBookException(String message){
            super(message);
        }
    }
    public static String[] books={"高数","线代","几何","生物","编程"};

    public static void main(String[] args) {

        System.out.println("序号.\t书名");
        for (int i=1;i<=5;i++){
            System.out.println(i+".\t\t"+books[i-1]);
        }
        LibrarySystem lib=new LibrarySystem();
        lib.test();
    }

    public void test(){
        try {
            System.out.println("请选择:1-按照序号查找图书;2-按照名称查找图书");
            int i = input();
            switch (i) {
                case 1:
                    bookNum();
                    break;
                case 2:
                    bookName();
                    break;
                case -1:
                    test();
                    break;
                default:
                    throw new NoBookException("请输入1或2:");
            }
        }
        catch(NoBookException e){
            System.out.println(e.getMessage());
            test();
        }
    }

    public void bookNum(){
            System.out.println("请输入图书序号:");
            try {
                int i = input();
                if (i > 0 & i <= books.length)
                    System.out.println(books[i-1]);
                else
                    throw new NoBookException("请输入正确的序号");
            }catch(NoBookException e){
                System.out.println(e.getMessage());
                bookNum();
            }
    }

    public void bookName(){
        Scanner sc = new Scanner(System.in);
        try {
            System.out.println("请输入书名:");
            String book= sc.next();
            boolean flag=false;
            for (String i:books) {
                if (book.equals(i)) {
                    flag=true;
                    System.out.println(i);
                    break;
                }
            }
            if(flag=false) {
                throw new NoBookException("请输入正确的书名:");
            }
        }catch (NoBookException e){
            System.out.println(e.getMessage());
            bookName();
        }catch (Exception e){
            e.printStackTrace();
            bookName();
        }
    }

    public int input(){
        Scanner sc = new Scanner(System.in);
        try {
            int i = sc.nextInt();
            return i;
        }catch (Exception e){
            System.out.println("请输入整数");
            sc=new Scanner(System.in);
            return -1;
        }
    }
}

第61行,当图书名称输入错误时不能重新执行bookName()方法,不知道哪出问题了