附加设置为 true 的 FileWriter 正在向文件写入两次 [关闭]

Question

当 FileWriter 将输出保存到文件时，它会保存两次。这是我的代码：

import java.io.*;
import java.util.Scanner;

public class Room {

    static Scanner keyboard = new Scanner(System.in);
    static int numberOfRooms;
    static String roomType;
    static char airCon;
    static char balcony;

    public static void addRoom() {

        System.out.println("How many rooms would you like to add at once?");
        numberOfRooms = keyboard.nextInt();

        System.out.println("Choose the type of room:\\nR for regular\\nD for deluxe\\nS for suite\\n-> ");
        roomType = keyboard.next();

        System.out.println("Does this room have air conditioning? [T/F]");
        airCon = keyboard.next().charAt(0);

        System.out.println("Does this room have a balcony? [T/F]");
        balcony = keyboard.next().charAt(0);

        System.out.println("Rooms have been added successfully to the system. To list them, press 2 in menu");

    }

    public static void roomsInit() {

        File myObj = new File("listOfRooms.txt");


        try {
            PrintWriter out = new PrintWriter(new FileWriter("listOfRooms.txt", true));

            for (int i = 1; i <= numberOfRooms; i++) {

                out.println("Room " + "#" + i + " " + roomType + " " + airCon + " " + balcony);
            }
            out.close();

        }
        catch (IOException ex)
        {
            //
        }

    }

}

我试着在 out.close() 之前放出 out.flush()。那没有用，它不尊重我的用户输入（numberOfRooms 变量）。

我希望我的

numberOfRooms.txt

文件看起来像这样：

Room #1 r t t
Room #2 r t t
Room #3 r t t
Room #4 r t t
Room #5 r t t

但它最终看起来像这样：

Room #1 r t t
Room #2 r t t
Room #3 r t t
Room #4 r t t
Room #5 r t t
Room #1 r t t
Room #2 r t t
Room #3 r t t
Room #4 r t t
Room #5 r t t

Answer 1

您两次看到输出的原因是您调用了 roomsInit() 方法两次，它使用 FileWriter 写入同一个文件。第一次它写入用户输入的房间数，第二次它再次写入相同的房间数，而不要求用户输入。

要解决此问题，您应该确保只调用一次roomsInit()，并确保在调用该方法之前初始化numberOfRooms变量。

实现此目的的一种方法是将 numberOfRooms 的用户输入代码移动到 roomsInit()，并将其从 addRoom() 中删除。然后，您可以调用 addRoom() 获取用户输入，并将 numberOfRooms 的值传递给 roomsInit() 以写入文件。这是一个如何修改代码的示例：

import java.io.*;
import java.util.Scanner;

public class Room {

    static Scanner keyboard = new Scanner(System.in);
    static int numberOfRooms;
    static String roomType;
    static char airCon;
    static char balcony;

    public static void addRoom() {

        System.out.println("Choose the type of room:\\nR for regular\\nD for deluxe\\nS for suite\\n-> ");
        roomType = keyboard.next();

        System.out.println("Does this room have air conditioning? [T/F]");
        airCon = keyboard.next().charAt(0);

        System.out.println("Does this room have a balcony? [T/F]");
        balcony = keyboard.next().charAt(0);

        System.out.println("Rooms have been added successfully to the system. To list them, press 2 in menu");
    }

    public static void roomsInit(int numberOfRooms) {

        try {
            PrintWriter out = new PrintWriter(new FileWriter("listOfRooms.txt", true));

            for (int i = 1; i <= numberOfRooms; i++) {
                out.println("Room " + "#" + i + " " + roomType + " " + airCon + " " + balcony);
            }
            out.close();

        }
        catch (IOException ex)
        {
            //
        }

    }

    public static void main(String[] args) {
        System.out.println("How many rooms would you like to add at once?");
        numberOfRooms = keyboard.nextInt();
        addRoom();
        roomsInit(numberOfRooms);
    }
}

在此修改版本中，main()方法首先询问用户要添加的房间数量，然后调用addRoom()获取每个房间的详细信息，最后调用roomsInit() numberOfRooms 变量将房间写入文件。

请注意，在此示例中，我已从 numberOfRooms 变量中删除了 static 修饰符，并将其作为参数传递给 roomsInit()。这是因为通常最好避免使用全局变量，并在方法之间显式传递数据。