Java:当用户输入名称时打开并输出文件

Question

我有一个家庭作业，需要根据用户输入的内容输出一个文本 ASCII 文件。我没有使用直接路径，因为当我将其交给教授时需要能够测试它，所以我在 src 文件夹中有文本文件，因此只能使用文件名。但是，当我尝试测试它时，我收到文件未找到错误。我知道我输入的文件名正确，但是我的代码中是否缺少某些内容导致了这种情况？我正在尝试测试该程序并确保它执行应有的所有操作，但我有点卡住了，因为我无法输出文件。这是我的代码:

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

class TileMap

{

/*
    FUNCTION NAME: Main ;
    INPUT: none.
    OUTPUT: a message to the user of this program, all of the
    prompts and a final display according to user specifications.
    PRECONDITIONS:  None.
    POSTCONDITIONS: Variables and calls made according to users input
                    output set to start on a new line.
    CALLERS: None.
    CALLES: askPermission, getParameters(), getImage(), and doTileJob().

*/

// Start of Main Function

    public static void main(String args[])
    {
        int MAXSIDE = 100;
        Scanner scan = new Scanner(System.in);
        char [][] buffer = new char [MAXSIDE][MAXSIDE];
        String fileName = "";
        int tilesAcross = 0;
        int tilesDown = 0;
        int imageHeight = 0;
        int imageWidth = 0;
        char userInput = 0;

        System.out.println("Would you like to tile an image in a file?");

        TileMap.askPermission(userInput);
        TileMap.getParameters(fileName, tilesAcross, tilesDown);
        TileMap.getImage(buffer, fileName, imageHeight, imageWidth);
        TileMap.doTileJob(buffer, fileName, tilesDown, tilesAcross, imageHeight, imageWidth);

    }

/*
    FUNCTION NAME: askPermission ;
    INPUT: none.
    OUTPUT: a message to the user of this program.
    PRECONDITIONS:  output set to start on a new line.
    POSTCONDITIONS: variable response has user's answer stored in it.
    CALLERS: the main program
    CALLES: None.

*/

    static boolean askPermission(char response)
        {
            char y = 0;
            Scanner scan = new Scanner(System.in);

            System.out.println("If yes, type a 'y', else type 'n':");
            response = scan.next().charAt(0);

            boolean yes = (response == y);

            if(yes = true)
                return true;
            else
                return false;
        }


/*
   FUNCTION NAME getParameters ;
   INPUT: the file name, number of tiles across and down.
   OUTPUT: message "Getting Image".
   PRECONDITIONS: the variable response has 'y' in it.
   POSTCONDITIONS: variables set with the values entered by user.
   CALLERS: the main program
   CALLEES: none
*/

    static void getParameters(String fileName, int tilesDown, int tilesAcross)
    {
        Scanner scan = new Scanner(System.in);

        System.out.println("Please enter the file name: ");
        fileName = scan.nextLine();
        File file = new File(fileName);
        System.out.println("Please enter the number of tiles across you want: ");
        tilesAcross = scan.nextInt();
        System.out.println("Please enter the number of tiles down you want: ");
        tilesDown = scan.nextInt();


        System.out.println("Getting Image...");

    }

/*
    FUNCTION NAME: getImage ;
    INPUT:the file name and the height and width of the pattern to be made.
    OUTPUT: the message "Getting Image".
    PRECONDITIONS: array for image declared, the variables fileName, 
                   imageHeight and imageWidth set with proper values.  
    POSTCONDITIONS: the image is stored in the array.
    CALLERS: the main program
    CALLEES: none
*/
    static void getImage(char [][] buffer,
                String fileName, int imageHeight, int imageWidth)
    {
        File file = new File(fileName);
        try
        {       
            Scanner fstream = new Scanner(file);

            imageHeight = fstream.nextInt();
            imageWidth = fstream.nextInt();
        }


        catch (Exception e)
        {
            System.err.println("Error: " + e.getMessage());
        }
    }

/*
    FUNCTION NAME: doTileJob;
    INPUT:the buffer with the image and the height and width of the
          pattern to be made, and the user's input for tilesAcross, and tilesDown.
    OUTPUT: the patterns structured according to users input.
    PRECONDITIONS: All of the variables are set and pattern is stored in 'buffer'.
    POSTCONDITIONS: Output displayed according to users input.
    CALLERS: the main program
    CALLEES: none
*/
//  This function uses for loops to display the images. The inner most for loop prints one line of the picture.

    static void doTileJob (char [] [] buffer , String fileName, int tilesDown, int tilesAcross, int imageHeight, int imageWidth)
        {
            buffer = new char[tilesDown][tilesAcross];

            for(int i=0; i < imageHeight; i++)
            {
                for(int w = 0; w < imageWidth; w++)
                {
                    System.out.println(fileName);
                    for(int t = 0; t < tilesAcross; t++)
                    {
                        for(int a = 0; a < tilesDown; a++)
                        {
                            System.out.println(fileName);
                        }
                    }
                }
            }





    }
}

Answer 1

不使用askPermission的返回值。您在方法中更新的字段是本地的，它们不会传回您的 main。

如果要访问类中的字段，则需要创建该类的实例。之后，您可以直接访问这些字段。像下面的代码这样的东西可能会更好地满足您的目的。

class TileMap    
{
    static final int MAXSIDE = 100;
    char [][] buffer = new char [MAXSIDE][MAXSIDE];
    String fileName = "";
    int tilesAcross = 0;
    int tilesDown = 0;
    int imageHeight = 0;
    int imageWidth = 0;
    char userInput = 0;

// Start of Main Function

    public static void main(String args[])
    {
        TileMap tileMap = new TileMap();
        tileMap.exec();
    }

    private void exec()
    {
        Scanner scan = new Scanner(System.in);
        System.out.println("Would you like to tile an image in a file?");

        if (askPermission()) {
          getParameters();
          getImage();
          doTileJob();
        }
    }

    // code without the static ...
}