通过Java

Question

我正在尝试使用此代码：

1. 首先阅读文本文件＆＃34; occupancy＆＃34 ;,将初始化为 10个零。

2. 将其分配给数组（guestsIn []）。

3. 从键盘输入获取新数据，并使用新值更新数组（guestsIn []）（有时会覆盖所有值，有时不会覆盖）

4. 覆盖文件上的新数组＆＃34;占用＆＃34;以10个int值的形式。

这是我运行此代码时收到的错误消息：

Exception in thread "main" java.util.NoSuchElementException

at java.util.Scanner.throwFor(Unknown Source)

at java.util.Scanner.next(Unknown Source)

at java.util.Scanner.nextInt(Unknown Source)

at java.util.Scanner.nextInt(Unknown Source)

at occupancyProg.main(occupancyProg.java:18)

最终，我正在尝试使用单个文本文件（仅包含10个int值）进行扫描和打印。 但我不知道错误信息告诉我什么，我不知道我的逻辑在哪里有缺陷。

据我理解

    PrintStream diskWriter = new PrintStream(new File("occupancy"));

应该创建一个文件＆＃34;占用＆＃34;因为在语句中使用了 new ，所以我修改了代码以便在覆盖过程中修复可能出现的问题（通过删除现有文件并将其替换为新文件），但是出现相同的错误消息。 非常感谢帮助。

import java.util.Scanner;
import java.io.File;
import java.io.FileNotFoundException;
import java.io.PrintStream;

public class occupancyProg {

public static void main(String[] args) 
            throws FileNotFoundException {

    Scanner diskScanner = new Scanner(new File("occupancy"));
    Scanner keyboard = new Scanner(System.in);
    PrintStream diskWriter = new PrintStream(new File("occupancy"));

    int guestsIn[] = new int[10];
    int whichRoom, numGuests;
        for (int roomNum= 0; roomNum<10; roomNum++) {
            guestsIn[roomNum] = diskScanner.nextInt(); 
            }

        do {
            System.out.print("Room Number: ");
            whichRoom = keyboard.nextInt();


            System.out.print("Number of Guests: ");
            numGuests = keyboard.nextInt();

            guestsIn[whichRoom]=numGuests;

            System.out.print("Do another? Y/N");

        } while(keyboard.findWithinHorizon(".", 0).charAt(0) == 'Y');

        new File("occupancy").delete();

        for (int roomNum= 0; roomNum<10; roomNum++) {
        diskWriter.print("guestsIn[whichRoom] ");
         }
        keyboard.close();
        diskScanner.close();

}

}

Answer 1

您似乎正在尝试同时打开文件进行读写。即使您在完成从diskScanner读取之后也没有写入diskWriter，只需构建diskWriter就会打开文件进行写入并截断文件。订单应该是：

• 打开diskScanner
• 从diskScanner中读取
• 关闭diskScanner
• open diskWriter
• 写入diskWriter
• 关闭diskWriter

不需要删除，因为打开相同的文件进行写入将替换它。

public static void main(String[] args) throws FileNotFoundException {
    Scanner diskScanner = new Scanner(new File("occupancy"));
    Scanner keyboard = new Scanner(System.in);

    int guestsIn[] = new int[10];
    int whichRoom, numGuests;
    for (int roomNum= 0; roomNum<10; roomNum++) {
        guestsIn[roomNum] = diskScanner.nextInt();
    }

    do {
        System.out.print("Room Number: ");
        whichRoom = keyboard.nextInt();

        System.out.print("Number of Guests: ");
        numGuests = keyboard.nextInt();

        guestsIn[whichRoom]=numGuests;

        System.out.print("Do another? Y/N");
    } while(keyboard.findWithinHorizon(".", 0).charAt(0) == 'Y');

    keyboard.close();
    diskScanner.close();

    PrintStream diskWriter = new PrintStream(new File("occupancy"));
    for (int roomNum= 0; roomNum<10; roomNum++) {
        diskWriter.print(guestsIn[roomNum]);
        diskWriter.print(' ');
    }
    diskWriter.close();
}