将对象以文本写入一个文件

Posted 2021-03-24 斯坦尼拉夫斯基

1.首先创建一个Mybook对象

public class MyBook {
    private String name;
    private String author;
    private LocalDate date;

    public MyBook(){

    }
    public MyBook(String name,String author,int year,int month,int day){
        this.name=name;
        this.author=author;
        this.date=LocalDate.of(year,month,day);
    }

    public String getName() {
        return name;
    }

    public String getAuthor() {
        return author;
    }

    public LocalDate getDate() {
        return date;
    }
}

2.写的操作

public class MyFileTest {

    public static void main(String[] args) throws FileNotFoundException {
        //初始化数组
        MyBook[] books=new MyBook[4];
        books[0]=new MyBook("coreJava","Unknown",2012,2,6);
        books[1]=new MyBook("coreJava","Unknown",2012,2,6);
        books[2]=new MyBook("coreJava","Unknown",2012,2,6);
        books[3]=new MyBook("coreJava","Unknown",2012,2,6);
        //写操作
        try(PrintWriter out=new PrintWriter(new FileOutputStream("book.txt"))){
            writeData(out,books);
        }
    }

    private static void writeData(PrintWriter out, MyBook[] books) {
        out.println(books.length);//输出有几个对象，后面的读要用到
        for (MyBook myBook:books){
            writeBook(out,myBook);
        }
    }

    private static void writeBook(PrintWriter out, MyBook myBook) {
        out.println(myBook.getName()+"|"+myBook.getAuthor()+"|"+myBook.getDate());
    }
}

Note：

1.PrintWriter对象：进行文本格式打印字符串和数字,是Writer的子类

　　常用的构造方法：PrintWriter(String fileName, String csn)/PrintWriter(OutputStream out)，这里采用的第二种，FileOutputStream是OutputStream的子类

2.带流的try{}：会在程序执行完成后自动执行close()

3.InputStream/OutputStream:读入/写入一个字节序列的输入输出流

   Reader/Writer：读写基于两个字节序列的char值

   一般读写操作使用它们的子类的读写放法，本例中，使用PrintWriter中的println()进行输出

4.FileInputStream/FileOutputStream 没有具体的读写文本的方法，（read(),write()只能读写单字节），它们的作用就是来获取流。

　　用流来构造具有相应功能的对象。