我在写作业的时候，出现了问题但是我不知道为什么会这样？这是一个借书系统

Question

//package jie_shu_xi_tong;import java.util.*;class LibrarySystem{ public static void main(String args[]){ System.out.println("001号借书系统为您服务请选择您要的服务："+"\n"+                   "(1)    按照书名查找"+"\n"+                   "(2)    按照图书序号查找"); } }public class BookData{/*这是问题     E:\java 笔记和错误\yuanwenjian\LibrarySystem.java:15: class BookData is public, should be declared in a file named BookData.java*/public class BookData{ String Bookdata[] = new String[2];//Bookdata代表图书资料，存储书本的名称 public BookData(){ Bookdata[0] = "孙子兵法"; Bookdata[1] = "黄帝内经"; } }public class BookFind extends BookData{/*这是问题      E:\java 笔记和错误\yuanwenjian\LibrarySystem.java:23: class BookFind is public, should be declared in a file named BookFind.javapublic class BookFind extends BookData{*/ public BookFind(String BF){ BookData B = new BookData(); for(int i=0;i<B.Bookdata.length;i++){ if(B.Bookdata[i].equale(BF)){/*这是问题E:\java 笔记和错误\yuanwenjian\LibrarySystem.java:28: cannot find symbolsymbol  : method equale(java.lang.String)location: class java.lang.String                        if(B.Bookdata[i].equale(BF)){*/ System.out.println("您要的书"); } } } }

Answer 1

java的类需要在单独文件中，入门必知哦