JAVA-從txt文件讀取整數並計算整數

Question

我需要以下代碼的幫助。 我想做的是編寫一個程序，該程序讀取文件並計算平均成績並將其打印出來。 我嘗試了幾種方法，例如將文本文件解析為並行數組，但是遇到了在成績末尾使用％字符的問題。 下面的程序也打算將整數相加，但輸出為“未找到數字”。

這是文本文件的片段（整個文件是14行類似的輸入）：

 Arthur Albert,74% Melissa Hay,72% William Jones,85% Rachel Lee,68% Joshua Planner,75% Jennifer Ranger,76% 

這是我到目前為止的內容：

final static String filename = "filesrc.txt";

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

          Scanner scan = null;
          File f = new File(filename);
          try {
             scan = new Scanner(f);
          } catch (FileNotFoundException e) {
             System.out.println("File not found.");
             System.exit(0);
          }

          int total = 0;
          boolean foundInts = false; //flag to see if there are any integers

          while (scan.hasNextLine()) { //Note change
             String currentLine = scan.nextLine();
             //split into words
             String words[] = currentLine.split(" ");

             //For each word in the line
             for(String str : words) {
                try {
                   int num = Integer.parseInt(str);
                   total += num;
                   foundInts = true;
                   System.out.println("Found: " + num);
                }catch(NumberFormatException nfe) { }; //word is not an integer, do nothing
             }
          } //end while 

          if(!foundInts)
             System.out.println("No numbers found.");
          else
             System.out.println("Total: " + total);

          // close the scanner
          scan.close();
       }            
}

任何幫助將非常感激！

Answer 1

這是固定代碼。 而不是使用分割輸入

" "

你應該使用

","

這樣，當您解析拆分的字符串時，可以使用substring方法並解析輸入的數字部分。

例如，給定字符串

Arthur Albert,74%

我的代碼會將其分為Arthur ALbert和74% 。 然后，我可以使用substring方法並解析74％的前兩個字符，這將得到74。

我以某種方式編寫代碼，以便它可以處理0到999之間的任何數字，並在添加您還沒有的添加內容時添加了注釋。 如果您仍然有任何疑問，請不要害怕問。

final static String filename = "filesrc.txt";

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

          Scanner scan = null;
          File f = new File(filename);
          try {
             scan = new Scanner(f);
          } catch (FileNotFoundException e) {
             System.out.println("File not found.");
             System.exit(0);
          }

          int total = 0;
          boolean foundInts = false; //flag to see if there are any integers
             int successful = 0; // I did this to keep track of the number of times
             //a grade is found so I can divide the sum by the number to get the average

          while (scan.hasNextLine()) { //Note change
             String currentLine = scan.nextLine();
             //split into words
             String words[] = currentLine.split(",");

             //For each word in the line
             for(String str : words) {
                 System.out.println(str);
                try {
                    int num = 0;
                    //Checks if a grade is between 0 and 9, inclusive
                    if(str.charAt(1) == '%') {
                        num = Integer.parseInt(str.substring(0,1));
                        successful++;
                        total += num;
                       foundInts = true;
                       System.out.println("Found: " + num);
                    }
                    //Checks if a grade is between 10 and 99, inclusive
                    else if(str.charAt(2) == '%') {
                        num = Integer.parseInt(str.substring(0,2));
                        successful++;
                        total += num;
                       foundInts = true;
                       System.out.println("Found: " + num);
                    }
                    //Checks if a grade is 100 or above, inclusive(obviously not above 999)
                    else if(str.charAt(3) == '%') {
                        num = Integer.parseInt(str.substring(0,3));
                        successful++;
                        total += num;
                       foundInts = true;
                       System.out.println("Found: " + num);
                    }
                }catch(NumberFormatException nfe) { }; //word is not an integer, do nothing
             }
          } //end while 

          if(!foundInts)
             System.out.println("No numbers found.");
          else
             System.out.println("Total: " + total/successful);

          // close the scanner
          scan.close();
       }

Answer 2

正則表達式 ： ^(?<name>[^,]+),(?<score>[^%]+)

細節：

• ^在行首處聲明位置
• (?<>)命名為捕獲組
• [^]匹配列表中不存在的單個字符
• +無限次匹配

Java代碼 ：

import java.util.regex.Pattern;
import java.util.regex.Matcher;

final static String filename = "C:\\text.txt";

public static void main(String[] args)  throws IOException 
{
    String text = new Scanner(new File(filename)).useDelimiter("\\A").next();
    final Matcher matches = Pattern.compile("^(?<name>[^,]+),(?<score>[^%]+)").matcher(text);

    int sum = 0;
    int count = 0;
    while (matches.find()) {
        sum += Integer.parseInt(matches.group("score"));
        count++;
    }

    System.out.println(String.format("Average: %s%%", sum / count));
}

輸出：

Avarege: 74%

Answer 3

如果只有少數幾行符合您指定的格式，則可以嘗試以下（IMO）不錯的功能解決方案：

double avg = Files.readAllLines(new File(filename).toPath())
            .stream()
            .map(s -> s.trim().split(",")[1]) // get the percentage
            .map(s -> s.substring(0, s.length() - 1)) // strip off the '%' char at the end
            .mapToInt(Integer::valueOf)
            .average()
            .orElseThrow(() -> new RuntimeException("Empty integer stream!"));

System.out.format("Average is %.2f", avg);

Answer 4

您的split方法是錯誤的，並且您沒有使用任何Pattern和Matcher來獲取int值。 這是一個工作示例：

private final static String filename = "marks.txt";

public static void main(String[] args) {
    // Init an int to store the values.
    int total = 0;

    // try-for method!
    try (BufferedReader reader = Files.newBufferedReader(Paths.get(filename))) {
        // Read line by line until there is no line to read.
        String line = null;
        while ((line = reader.readLine()) != null) {
            // Get the numbers only uisng regex
            int getNumber = Integer.parseInt(
                    line.replaceAll("[^0-9]", "").trim());
            // Add up the total.
            total += getNumber;
        }
    } catch (IOException e) {
        System.out.println("File not found.");
        e.printStackTrace();
    }
    // Print the total only, you know how to do the avg.
    System.out.println(total);
}

Answer 5

您可以通過以下方式更改代碼：

     Matcher m;
     int total = 0;
     final String PATTERN = "(?<=,)\\d+(?=%)";
     int count=0;
     while (scan.hasNextLine()) { //Note change
        String currentLine = scan.nextLine();
        //split into words
        m =  Pattern.compile(PATTERN).matcher(currentLine);
        while(m.find())
        {
            int num = Integer.parseInt(m.group());
            total += num;
            count++;
        }
     } 

     System.out.println("Total: " + total);
     if(count>0)
         System.out.println("Average: " + total/count + "%");

對於您的輸入，輸出為

Total: 450
Average: 75%

說明：

我正在使用以下正則表達式(?<=,)\\\\d+(?=%) n從每行中提取,和%字符之間的數字。

正則表達式用法： https : //regex101.com/r/t4yLzG/1