在 Java 中读取（分配）txt.file 个值

Question

更新： 我使用 '\n' 来改变 saveGame 方法中的每一行，这是在 API 中指定的。这意味着 readLine 应该正确地找到文件中的每一行，分配它的值并在读取最后一行后关闭。但是，我仍然得到 "null" (NullPointerException) 作为输出...

这就是在 API 中指定 null 的方式：

(readLine) Returns:

A String containing the contents of the line, not including any line-termination characters, or null if the end of the stream has been reached

我正在尝试读取一个 txt 文件并将其行分配到一个 int [][] 数组中。

这是我的 savegame.txt 文件的示例：

每一行代表一个整数值。我的 saveGame 方法将数组 "gameBoard" 的当前 int 值写入上面显示的文件中。此示例表示以下游戏状态：

  |   | O

  | X | O

X |   |

但是，当我尝试使用我的 loadGame 方法读取 savegame.txt 文件时，该方法将每个单独的游戏板位置 [0][0] 分配给 [2][2] 各自的值，我得到null 作为输出，游戏以空数组开始。根据我的逻辑，我的 loadGame 方法应该单独读取每一行并将其字符串值解析为一个整数，然后我的 int[][] 数组 gameBoard 可以解释该整数。 我想知道为什么这不能正常工作。

FileManagement.class

package storagePack;

import structurePack.Board;

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

/**
 * The FileManagement-Class is responsible for the saving and loading of gamedata.
 * It saves the current gameBoard and reads it with the loadGame Method.
 */

public class FileManagement {
    static String filename = "Savegame.txt";

/**
 * Schema:
 * (0,0) | (0,1) | (0,2)
 * (1,0) | (1,1) | (1,2)
 * (2,0) | (2,1) | (2,2)
 */
/**
 * @param gameBoard, the currently active Array from the Board.class.
 * @throws Exception, FileNotFoundException
 */
public static void saveGame(int[][] gameBoard) throws Exception {
    //serialization
    PrintWriter writer;
    try {

        writer = new PrintWriter(new FileOutputStream(filename), false);
        for (int i = 0; i < gameBoard.length; i++) {
            for (int j = 0; j < gameBoard.length; j++) {
                int entry = gameBoard[i][j];
                writer.print(entry);
                writer.println('\n');
            }

        }
        writer.close();
    } catch (Exception e) {
        System.out.println(e.getMessage());
    }
}

/**
 * @throws Exception, FileNotFoundException
 */
public static void loadGame() throws Exception {
    //deserialization
    FileReader fileReader = new FileReader(filename);
    BufferedReader bufferedReader = new BufferedReader (fileReader);
    try {
        structurePack.Board.gameBoard[0][0] = Integer.parseInt(bufferedReader.readLine());
        structurePack.Board.gameBoard[0][1] = Integer.parseInt(bufferedReader.readLine());
        structurePack.Board.gameBoard[0][2] = Integer.parseInt(bufferedReader.readLine());
        structurePack.Board.gameBoard[1][0] = Integer.parseInt(bufferedReader.readLine());
        structurePack.Board.gameBoard[1][1] = Integer.parseInt(bufferedReader.readLine());
        structurePack.Board.gameBoard[1][2] = Integer.parseInt(bufferedReader.readLine());
        structurePack.Board.gameBoard[2][0] = Integer.parseInt(bufferedReader.readLine());
        structurePack.Board.gameBoard[2][1] = Integer.parseInt(bufferedReader.readLine());
        structurePack.Board.gameBoard[2][2] = Integer.parseInt(bufferedReader.readLine());
        fileReader.close();
        bufferedReader.close();

    } catch (Exception e) {
        System.out.println(e.getMessage());
    }
}
}

readLine API-文档

public String readLine()
                throws IOException

Reads a line of text. A line is considered to be terminated by any one of a line feed ('\n'), a carriage return ('\r'), or a carriage return followed immediately by a linefeed.

Returns:
A String containing the contents of the line, not including any line-termination characters, or null if the end of the stream has been reached

Throws:
IOException - If an I/O error occurs

See Also:
Files.readAllLines(java.nio.file.Path, java.nio.charset.Charset)

Answer 1

请更改loadGame方法如下：

public static void loadGame() throws Exception {
    //deserialization

    FileReader fileReader = new FileReader(filename);
    BufferedReader bufferedReader = new BufferedReader(fileReader);
    structurePack.Board.gameBoard[0][0] = Integer.parseInt(bufferedReader.readLine());
    structurePack.Board.gameBoard[0][1] = Integer.parseInt(bufferedReader.readLine());
    structurePack.Board.gameBoard[0][2] = Integer.parseInt(bufferedReader.readLine());
    structurePack.Board.gameBoard[1][0] = Integer.parseInt(bufferedReader.readLine());
    structurePack.Board.gameBoard[1][1] = Integer.parseInt(bufferedReader.readLine());
    structurePack.Board.gameBoard[1][2] = Integer.parseInt(bufferedReader.readLine());
    structurePack.Board.gameBoard[2][0] = Integer.parseInt(bufferedReader.readLine());
    structurePack.Board.gameBoard[2][1] = Integer.parseInt(bufferedReader.readLine());
    structurePack.Board.gameBoard[2][2] = Integer.parseInt(bufferedReader.readLine());
}

此代码可能适合您。

在 Java 中读取（分配）txt.file 个值

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