Java基础案例教程 第七章IO（输入输出）———【任务7-1】保存书店每日交易记录 （字节流）

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 public static ArrayList<Books> booksList = new ArrayList<Books>();

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 /*
    * 初始化书架上的图书信息，添加几本书
    * */
    public static void  init (ArrayList<Books> books){
        Books book1 = new Books(101, "数据结构", 91, 100, "清华出版社");
        Books book2 = new Books(102, "组成原理", 92, 200, "西北出版社");
        Books book3 = new Books(103, "操作系统", 93, 300, "华大出版社");
        books.add(book1);
        books.add(book2);
        books.add(book3);
    }

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//用户提示
Scanner sc=new Scanner(System.in);
System.out.print("请输入图书编号:");
int bookId=sc.nextInt();

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 Date date=new Date();
 DateFormat format =new SimpleDateFormat("yyyyMMdd");

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//追加写入
BufferedOutputStream out = new BufferedOutputStream(new FileOutputStream("D:\IDEA-file\"+fileName, true));
String str = sbf.toString();
byte[] b = str.getBytes();
out.write(b);



FileOutputStream --> BufferedOutputStream --> out.write(b[i]) --> byte[] b = str.getBytes() -->
String str = stringBufferStr.toString();

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package cn.itcast.task01;

/**
 * @author wangyue
 * @version 1.0
 * @date 2019/7/1 14:42
 * @describe: 图书类
 */
public class Books {
    //内部变量
    private int id;
    private String name;
    private double price;
    private int number;
    // private double totalPrice;
    private String press; //出版社

    //构造方法
    public Books() {
    }

    public Books(int id, String name, double price, int number, String press) {
        this.id = id;
        this.name = name;
        this.price = price;
        this.number = number;
        //this.totalPrice = totalPrice;
        this.press = press;
    }

    //Get and  Set
    public int getId() {
        return id;
    }

    public void setId(int id) {
        this.id = id;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public double getPrice() {
        return price;
    }

    public void setPrice(double price) {
        this.price = price;
    }

    public int getNumber() {
        return number;
    }

    public void setNumber(int number) {
        this.number = number;
    }

   /* public double getTotalPrice() {
        return totalPrice;
    }

    public void setTotalPrice(double totalPrice) {
        this.totalPrice = totalPrice;
    }*/

    public String getPress() {
        return press;
    }

    public void setPress(String press) {
        this.press = press;
    }

    @Override
    public String toString() {
        return "图书编号：" + id +
                "   图书名称：" + name +
                "   出版社：" + press +
                "   单价：" + price +
                "   库存数量：" + number;
    }
}

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package cn.itcast.task01;

import java.util.ArrayList;
import java.util.Scanner;

/**
 * @author wangyue
 * @version 1.0
 * @date 2019/7/1 14:42
 * @describe: 销售图书实现类
 */
public class SellBooks {
    //建立书架
    public static ArrayList<Books> booksList = new ArrayList<Books>();

    public static void main(String[] args) {
        //实例化书架
        init(booksList);
        //把书架上所有图书信息打印出来
        for (Books book : booksList) {
            System.out.println(book);
        }
        //销售图书
        while (true) {
            Scanner sc = new Scanner(System.in);
            //用户提示
            System.out.print("请输入图书编号:");
            int bookId = sc.nextInt();
            //获取图书库存信息
            Books book = getBookInfo(bookId);
            if (book == null) {
                System.out.println("输入图书编码有误");
            } else {
                System.out.println(book);
                System.out.print("请输入购买数量：");
                int buyNumber = sc.nextInt();
                if (buyNumber > book.getNumber()) {    //数量不足
                    System.out.println("库存不足");
                } else {   //库存数量足够

                    //封装Books对象
                    Books sellBook = new Books(bookId, book.getName(), book.getPrice(), book.getNumber(), book.getPress());
                    //保存销售记录
                    FileUnit.saveRecord(sellBook);

                    //修改库存
                    book.setNumber(book.getNumber() - buyNumber);
                    System.out.println("当前的库存状况");
                    System.out.println(book);
                }
            }

        }


    }

    /*
     * 初始化书架上的图书信息，添加几本书
     * */
    public static void init(ArrayList<Books> books) {
        Books book1 = new Books(101, "数据结构", 91, 100, "清华出版社");
        Books book2 = new Books(102, "组成原理", 92, 200, "西北出版社");
        Books book3 = new Books(103, "操作系统", 93, 300, "华大出版社");
        books.add(book1);
        books.add(book2);
        books.add(book3);
    }


    public static Books getBookInfo(int bookId) {

        for (Books thisBook : booksList) {
            if (thisBook.getId() == bookId) {
                return thisBook;
            }
        }
        return null;

    }
}

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package cn.itcast.task01;

//import org.omg.CORBA.portable.InputStream;

import java.io.*;
import java.text.DateFormat;
import java.text.SimpleDateFormat;
import java.util.Date;

/**
 * @author wangyue
 * @version 1.0
 * @date 2019/7/2 14:07
 * @describe: 文件工具类
 */
public class FileUnit {
    public static final String SEPERATE_FIELD = ",";  //字段分割符，逗号
    public static final String SEPERATE_LINE = "rn";  //行分割符

    /*
     * 根据传进来的对象，保存一条记录
     */
    public static void saveRecord(Books book) {
        //检查今天的记录文件是否已存在
        Date date = new Date();
        DateFormat format = new SimpleDateFormat("yyyyMMdd");
        String fileName = "销售记录" + format.format(date) + ".csv";
        try {
            FileInputStream in = new FileInputStream("D:\IDEA-file\" + fileName);
            if (in != null) { //存在该文件，追加写入
                createRecord(fileName, true, book);
            }
        } catch (FileNotFoundException e) { //输入流获取失败，即不存在该文件，创建新的文件
            createRecord(fileName, false, book);
        } catch (IOException e) {
            e.printStackTrace();
        }
    }

    /**
     * 将图书的销售信息保存到记录文档里，同label来判断是修改还是新建
     *
     * @param fileName 保存的记录文件名
     * @param label    true：已存在只修改   false：新创建文件
     * @param book     记录对象
     */
    public static void createRecord(String fileName, boolean label, Books book) {
        BufferedOutputStream out = null;
        StringBuffer sbf = new StringBuffer(); //拼接字符串

        //多个创建输出流的地方，都需要try...catch  ,可以在最外围放一个，包含所有
        try {
            if (label) { //直接追加即可
                //创建输出流，用于追加文件 !!!
                out = new BufferedOutputStream(new FileOutputStream("D:\IDEA-file\" + fileName, true));
            } else { //不存在当天文件，新建一个
                out = new BufferedOutputStream(new FileOutputStream("D:\IDEA-file\" + fileName));
                //新文件需要创建表头
                String[] fieldSort = new String[]{"图书编号", "图书名称", "购买数量", "单价", "总价", "出版社"};
                for (String fieldKey : fieldSort) {
                    sbf.append(fieldKey).append(SEPERATE_FIELD);
                }
            }
            //购买记录的主体内容
            sbf.append(SEPERATE_LINE); //追加换行符
            sbf.append(book.getId()).append(SEPERATE_FIELD);
            sbf.append(book.getName()).append(SEPERATE_FIELD);
            sbf.append(book.getNumber()).append(SEPERATE_FIELD);
            sbf.append(book.getPrice()).append(SEPERATE_FIELD);
            sbf.append(book.getNumber() * book.getPrice()).append(SEPERATE_FIELD);
            sbf.append(book.getPress()).append(SEPERATE_FIELD);

            //写入文件
            String str = sbf.toString();
            byte[] b = str.getBytes();
            out.write(b);

        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            try {
                out.close();
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
    }


}