类定义（课下选做）

1、设计思路

1.根据题目要求覆盖（Override）toString方法、覆盖equals方法，即重写这两个方法；
2.根据题目要求定义至少三个构造方法，接收并初始化这些数据；
3.创建一个测试类Bookshelf, 其中的main方法创建并更新几个Book对象,并对产生的对象进行测试。

2、设计代码

Book.java

public class Book {String name;String writter;String publish;String date;Book(){    //定义第一个构造方法将所有元素初始化name=null;writter=null;publish=null;date=null;}Book(String name,String writter,String publish,String date){    //定义第二种构造方法给所有元素赋值this.name=name;this.writter=writter;this.publish=publish;this.date=date;}Book(String book[]){    //定义第三种构造方法用数组给元素赋值this.name=book[0];this.writter=book[1];this.publish=book[2];this.date=book[3];}public void setName(String name){this.name=name;}public String getName(){return name;}public void setWritter(String writter){this.writter=writter;}public String getWritter(){return writter;}public void setPublish(String publish){this.publish=publish;}public String getPublish(){return publish;}public void setDate(String date){this.date=date;}public String getDate(){return date;}public String toString(){    //重写toString（）方法return "书名："+name+"，作者："+writter+"，出版社："+publish+"，出版日期："+date;}public boolean equals(Object x){   //重写equals（）方法if(this==x)      //判断地址是否相等return true;if(x==null)      //判断对象是否为空return false;if (getClass()!=x.getClass())     //判断对象类型是否相等return false;Book book = (Book)x;     //上转型对象，判断子类成员变量是否相等if(book.name==this.name&&book.writter==this.writter&&book.publish==this.publish&&book.date==this.date)return true;elsereturn false;}
}

BookShelf.java

import java.util.*;
public class BookShelf {public static void main(String[] args){Book b0=new Book("Java","耿祥义","清华大学出版社","2017");Book b1=new Book("汇编语言与程序设计","钱晓捷","电子工业出版社","2018");Book b2=new Book("密码学","郑秀林","金城出版社","2016");Scanner reader=new Scanner(System.in);String s=null;System.out.println("进入书柜，请输入书名：");s=reader.nextLine();if(s.equals("Java")){System.out.println(b0);System.out.println(b0.equals(b0));}else if(s.equals("汇编语言与程序设计")){System.out.println(b1);System.out.println(b1.equals(b1));}else if(s.equals("密码学")){System.out.println(b2);System.out.println(b2.equals(b2));}else{System.out.println("书柜中无此书籍！");System.out.println(b0.equals(b2));}}
}