1、初始化

package Tasktwo;import java.util.ArrayList;
import java.util.Scanner;public class bookself {static ArrayList<book> bookself=new ArrayList();
public static void main(String[] args) {	insert();//初始化数据while(true) {Scanner in=new Scanner(System.in);System.out.println("请输入要购买的图书编号：");int bookid=in.nextInt();book selfbookid=chack(bookid);if(selfbookid!=null) {System.out.println("请输入要购买图书的数量：");int selfnumber=in.nextInt();if(selfnumber<=selfbookid.getNumber()) {//对购买的数据将进行打包book book1=new book(selfbookid.getId(),selfbookid.getBookname(),selfbookid.getNumber(),selfbookid.getPrice(),selfbookid.getSumprice(),selfbookid.getPublish());alter.databses(book1);//把打包购买的图书封装selfbookid.setNumber(selfbookid.getNumber()-selfnumber);for (Object object : bookself) {System.out.println(object);}System.out.println("已经进行打包完成");}else {System.out.println("数量不足");}}else {System.out.println("输入图书编号错误,请重新输入");}}
}
private static book chack(int bookid) {//检测有没有该idfor(int i=0;i<bookself.size();i++) {book book1=bookself.get(i);//取出里面的每一个集合if(book1.getId()==bookid) {return book1;// 饭返回一个集合}}return null;}private static void insert() { //初始化// TODO Auto-generated method stubbook book=new book(101,"java基础教程",100,45.8,45.8*100,"新华出版社");book book1=new book(202,"mySQL",50,123,123*50,"人民出版社");book book2=new book(303,"javascirpt",80,88.8,80*88.8,"新华出版社");bookself.add(book);                          bookself.add(book1);bookself.add(book2);for (Object object : bookself) {System.out.println(object);}
}}

封装

package Tasktwo;public class book {
int id;
private String bookname;
private int number;
private double price;
private double sumprice;
private String publish;public book(int id, String bookname, int number, double price, double sumprice, String publish) {super();this.id = id;this.bookname = bookname;this.number = number;this.price = price;this.sumprice = sumprice;this.publish = publish;}public book() {super();// TODO Auto-generated constructor stub}/*** @return the id*/public int getId() {return id;}@Overridepublic String  toString() {return "图片编号:"+id+"   图书名字:"+bookname+"    数量："+number+"   单价:"+price+ "总价："+sumprice+" 出版社："+publish;}/*** @param id the id to set*/public void setId(int id) {this.id = id;}/*** @return the bookname*/public String getBookname() {return bookname;}/*** @param bookname the bookname to set*/public void setBookname(String bookname) {this.bookname = bookname;}/*** @return the number*/public int getNumber() {return number;}/*** @param number the number to set*/public void setNumber(int number) {this.number = number;}/*** @return the price*/public double getPrice() {return price;}/*** @param price the price to set*/public void setPrice(double price) {this.price = price;}/*** @return the sumprice*/public double getSumprice() {return sumprice;}/*** @param sumprice the sumprice to set*/public void setSumprice(double sumprice) {this.sumprice = sumprice;}/*** @return the publish*/public String getPublish() {return publish;}/*** @param publish the publish to set*/public void setPublish(String publish) {this.publish = publish;}}

3、输入流写入

package Tasktwo;import java.io.BufferedOutputStream;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.text.DateFormat;
import java.text.SimpleDateFormat;
import java.util.Date;public class alter {public static void databses(book book1) {Date date=new Date();//
//		System.out.println(date);DateFormat time=new SimpleDateFormat("yyyyMMdd");//初始化格式time.format(date);String string=time.format(date);
//	    System.out.println(string);String csvname="销售表"+string+".csv";InputStream in=null;try {	in=new FileInputStream(csvname);  //有这张表System.out.println(in);//测试为不为空if(in!=null) {in.close();writerdabases(csvname,true,book1);//进行写入数据}} catch (FileNotFoundException e) {//没有这张表// TODO Auto-generated catch blockwriterdabases(csvname,false,book1);//进行写入数据} catch (IOException e) {// TODO Auto-generated catch blockSystem.out.println("写入异常");}}private static void writerdabases(String csvname, boolean b, book book1) {BufferedOutputStream out=null;StringBuffer sbf=new StringBuffer(); 	try {if(b) {out =new BufferedOutputStream(new FileOutputStream(csvname,true));}else {out =new BufferedOutputStream(new FileOutputStream(csvname));String []filesort=new String[] {"图书编号","图书名字","图书数量","图书单价","图书总价","图书出版社"};for(int i=0;i<filesort.length;i++) {sbf.append(filesort[i]).append(",");//这里可以改为全局的System.out.println(i);}}sbf.append("\r\n");sbf.append(book1.id).append(",");sbf.append(book1.getBookname()).append(",");sbf.append(book1.getNumber()).append(",");sbf.append(book1.getPrice()).append(",");sbf.append(book1.getSumprice()).append(",");sbf.append(book1.getPublish()).append(",");
//			下面进行写入String str=sbf.toString();//转化为字符串byte[]w=str.getBytes();out.write(w);} catch (IOException e) {// TODO Auto-generated catch blockSystem.out.println("异常2");} finally {if(out!=null) {try {out.close();} catch (IOException e) {// TODO Auto-generated catch blocke.printStackTrace();}}}
}
}