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在Java中读取（分配）txt.file值(Reading (assigning) txt.file values in Java)

 更新：我使用'\ n'来区分saveGame方法中的每一行，该方法在API中指定。 这意味着readLine应正确查找文件中的每一行，分配其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...  
 这是在API中指定null的方式：  
 
  （readLine）返回：  
  包含行内容的String，不包括任何行终止字符;如果已到达流的末尾，则为null  
 
 
 我正在尝试读取txt文件并将其行分配到int [] []数组中。  
 这是我的savegame.txt文件的示例：  
0 

0

-1

0

1

-1

1

0

0
 
 每一行代表一个int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gameBoard-position [0] [0]分配给[2] [2]各自的值，我得到null作为输出并且游戏开始用一个空数组。 从我的逻辑来看，我的loadGame方法应该单独读取每一行并将其String-value解析为一个Integer，而我的int [] []数组gameBoard可以解释它。 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)

Update: I'm using '\n' to diverse each line in the saveGame method, which is specified in the API. This means readLine should correctly find each individual line in the file, assign its value and close after it has read the last line. However, I still get "null" (NullPointerException) as output... 
This is how null is specified in the API: 
 
 (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 
 
 
I'm trying to read a txt file and assign its lines into an int [][] array. 
This is an example on how my savegame.txt file looks like: 
0 

0

-1

0

1

-1

1

0

0
 
Every line represents a int-value. My saveGame method writes the current int-values of the array "gameBoard" into the above shown file. This example represents the following game state: 
  |   | O 
 
 
  | X | O
 
 
X |   |  
 
 
However, when I try to read the savegame.txt file with my loadGame method, which assigns each individual gameBoard-position [0][0] to [2][2] its respective values, I get null as output and the game starts with an empty array. From my logic, my loadGame method should read every line seperately and parse its String-value into an Integer which than can be interpreted by my int[][] array gameBoard. I wonder why this does not work correctly.  
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-Documentation 
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)

原文：https://stackoverflow.com/questions/37322476

更新时间：2022-08-29 12:08

最满意答案

 目前还不完全清楚你要求的是什么，但听起来你试图在达到一定条件之前加上延迟，并同时返回触发条件的记录。  
 您可以像使用Enumerable#detect那样接近它，但是通过保持一个标记：  
def next_event_info
  next_event = nil
  delay = 0

  events.detect do |event|
    case (self.event_status(event))
    when "no status"
      true
    else
      delay += contact.event_delay(event)
      false
    end
  end

  [ next_event, delay ]
end
 
 更新如果您想要为所有事件添加所有延迟，还要查找状态为"no status"的第一个事件：  
def next_event_info
  next_event = nil
  delay = 0.0

  events.each do |event|
    case (self.event_status(event))
    when "no status"
      # Only assign to next_event if it has not been previously
      # assigned in this method call.
      next_event ||= event
    end

    # Tally up the delays for all events, converting to floating
    # point to ensure they're not native DB number types.
    delay += contact.event_delay(event).to_f
  end

  {
    :event => next_event,
    :delay => delay
  }
end
 
 这将为您提供一个Hash作为回报，您可以询问info[:event]或info[:delay] 。 请记住不要滥用此方法，例如：  
# Each of these makes a method call, which is somewhat expensive
next_event = next_event_info[:event]
delay_to_event = next_event_info[:delay]
 
 这将对此方法进行两次调用，这两次调用将迭代所有记录并进行计算。 如果你需要以这种方式使用它，你也可以为每个操作创建一个特殊用途的函数，或者将结果缓存到一个变量中并使用它：  
# Make the method call once, save the results
event_info = next_event_info

# Use these results as required
next_event = event_info[:event]
delay_to_event = event_info[:delay]

It's not entirely clear what you're asking for, but it sounds like you're trying to add up a delay until you reach a certain condition, and return the record that triggered the condition at the same time. 
You might approach that using Enumerable#detect like you have, but by keeping a tally on the side: 
def next_event_info
  next_event = nil
  delay = 0

  events.detect do |event|
    case (self.event_status(event))
    when "no status"
      true
    else
      delay += contact.event_delay(event)
      false
    end
  end

  [ next_event, delay ]
end
 
Update for if you want to add up all delays for all events, but also find the first event with the status of "no status": 
def next_event_info
  next_event = nil
  delay = 0.0

  events.each do |event|
    case (self.event_status(event))
    when "no status"
      # Only assign to next_event if it has not been previously
      # assigned in this method call.
      next_event ||= event
    end

    # Tally up the delays for all events, converting to floating
    # point to ensure they're not native DB number types.
    delay += contact.event_delay(event).to_f
  end

  {
    :event => next_event,
    :delay => delay
  }
end
 
This will give you a Hash in return that you can interrogate as info[:event] or info[:delay]. Keep in mind to not abuse this method, for example: 
# Each of these makes a method call, which is somewhat expensive
next_event = next_event_info[:event]
delay_to_event = next_event_info[:delay]
 
This will make two calls to this method, both of which will iterate over all the records and do the calculations. If you need to use it this way, you might as well make a special purpose function for each operation, or cache the result in a variable and use that: 
# Make the method call once, save the results
event_info = next_event_info

# Use these results as required
next_event = event_info[:event]
delay_to_event = event_info[:delay]

在Java中读取（分配）txt.file值(Reading (assigning) txt.file values in Java)

最满意答案

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