[Java 入门第三季 1-9]参考各位前辈后的作业

查书系统
主要代码分成两个部分，一个是main类，另外一个是书籍登记系统类。欢迎指导错误。在此感谢被我参考过的前辈们。

//main类

public class MainSystem {

    public static void main(String[] args) {
        // TODO Auto-generated method stub
        Book booksystem = new Book();
        booksystem.initBookDatas();
        booksystem.MainInterface();
    }
}   

//书籍登记系统类
import java.util.Scanner;

public class Book{
        private String[] BookDatas = new String[5];
        public void initBookDatas(){
            BookDatas[0] = "JavaSE";
            BookDatas[1] = "Java";
            BookDatas[2] = "Network";
            BookDatas[3] = "MySQL";
            BookDatas[4] = "Algorithm";
        }

        public void MainInterface(){
            try{
                int flag = 0;
                while(flag == 0){
                    System.out.println("输入命令：1.按照名称查找  2.按照序号查找 0.退出程序");
                    Scanner sc = new Scanner(System.in);
                    int result = sc.nextInt();
                    if(result == 1)
                        NameSearch();
                    else if(result == 2)
                        NumSearch();
                    else if(result == 0) {
                        flag = 1;
                    }
                    else{
                        throw new CommandException();
                    }
                }
                System.out.println("欢迎再次使用系统");
            }catch(StringException e){
                System.out.println("命令输入错误，请根据提示输入名称");
                MainInterface();
            }catch(IntException e){
                System.out.println("命令输入错误，请根据提示输入序号");
                MainInterface();
            }catch(CommandException e){
                System.out.println("命令输入错误，请根据提示输入指令序号");
                MainInterface();
            }

        }

        public void NameSearch() throws StringException{
            System.out.println("请输入图书名称：");
            Scanner in = new Scanner(System.in);
            String name = in.next();
            for(String bookName:BookDatas){
                if(bookName.equals(name)){
                    System.out.println("您所找的书为：" + name);
                    return;
                }
            }
            throw new StringException("输入书名无效");
        }

        public void NumSearch() throws IntException{
            System.out.println("请输入图书序号：");
            Scanner in = new Scanner(System.in);
                int num = in.nextInt();
                if(num>0 && num<5)
                    System.out.println("您所找的书为："+ BookDatas[num]);
                else
                    throw new IntException("输入序号无效");
        }

    }

    class StringException extends Exception{
        public StringException(){}
        public StringException(String message){
            super(message);
        }
    }

    class IntException extends Exception{
        public IntException(){}
        public IntException(String message){
            super(message);
        }       
    }

    class CommandException extends Exception{
        public CommandException(){}
        public CommandException(String message){
            super(message);
        }
    }