將對象以文本寫入一個文件，再讀取並在控制檯輸出

1.首先建立一個Mybook對象

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.寫的操做

public class MyFileTest {

    public static void main(String[] args) throws FileNotFoundException {
        //初始化數組
        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);
        //寫操做
        try(PrintWriter out=new PrintWriter(new FileOutputStream("book.txt"))){
            writeData(out,books);
        }
    }

    private static void writeData(PrintWriter out, MyBook[] books) {
        out.println(books.length);
        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對象：進行文本格式打印字符串和數字,是Writer的子類

　　　　經常使用的構造方法：PrintWriter(String fileName, String csn)/PrintWriter(OutputStream out)，這裏採用的第二種，FileOutputStream是OutputStream的子類

　　2.帶流的try{}：會在程序執行完成後自動執行close()

　　3.InputStream/OutputStream:讀入/寫入一個字節序列的輸入輸出流

  　　 Reader/Writer：讀寫基於兩個字節序列的char值

  　　 通常讀寫操做使用它們的子類的讀寫放法，本例中，使用PrintWriter中的println()進行輸出

　　4.FileInputStream/FileOutputStream 沒有具體的讀寫文本的方法，（read(),write()只能讀寫單字節），它們的做用就是來獲取流，用流來構造具備相應讀寫功能的對象。

3.讀操做

public class MyReaderFileTest {
    public static void main(String[] args) throws FileNotFoundException {
        //獲取文件流
        FileInputStream fis=new FileInputStream("employee.txt");
        //構建有讀文本功能的對象
        try(Scanner in=new Scanner(fis,"utf-8")){
            MyBook[] myBooks=readData(in);
            for (MyBook myBook:myBooks){
                System.out.println(myBook);
            }
        }
    }

    private static MyBook[] readData(Scanner in) {
        int n=in.nextInt();//有4個數據
        in.nextLine();
        MyBook[] myBooks=new MyBook[n];
        for (int i=0;i<n;i++){
            myBooks[i]=readBook(in);
        }
        return myBooks;
    }

    private static MyBook readBook(Scanner in) {
        String line=in.nextLine();
        String[] strs=line.split("\\|");//將以‘|’分開的部分組裝爲一個數組
        String name=strs[0];
        String author=strs[1];
        LocalDate date=LocalDate.parse(strs[2]);
        int year=date.getYear();
        int month=date.getMonthValue();
        int day=date.getDayOfMonth();
        return new MyBook(name,author,year,month,day);
    }

}

 

成功讀取！代碼是CoreJava這本書上的，不得不說人家這代碼寫的真心溜！