java - 在 Java 中读取输入文件并写入输出文件

Question

我目前正在上 Java 类(class)的最后一周，我们的最终项目要求我们让程序从输入 CSV 文件中的单个单元格读取数字和运算符(以逗号分隔)，让程序执行数学(从我选择的任何数字开始，然后让程序将结果写入输出 CSV 文件中。我有代码到转换错误，但我确信这是我最不用担心的。我对 Java 的理解很初级，我的类(class)几乎不及格。我只是认为我没有编程的头脑，我已经向教授表达了这一点。所以希望我能在这个最终项目上做得足够好，以提高我的成绩。不用了也就是说，我将立即放弃这个学位计划。

-迈克

这就是教授希望输出的样子:

添加2个总计2

添加6个，总共8个

总共减去9-1

乘以 10 总计 -10

元素数量 = 4，总数 = -10，平均值 = -2.5

错误如下:csvRead2.java:37:错误:类型不兼容:int 无法转换为 String number[i] = (Integer.parseInt(value[0]));//从字符串更改为整数。 ^

import java.io.*;

public class csvRead2 {
   public static void main(String args[]) {

      String operator[];
      String number[];
      String total;
      int i;

      // The name of the file to open.
      String inputFile = "mathInput.csv";

      // This will reference one line at a time
      String line = null;

      try { // start monitoring code for Exceptions
         // FileReader reads text files in the default encoding.
         FileReader read = new FileReader("mathInput.csv");
         // Always wrap FileReader in BufferedReader.
         BufferedReader buffRead = new BufferedReader(read);

         // Assume default encoding.
         FileWriter write = new FileWriter("mathOuput.csv", true); // true for append
         // Always wrap FileWriter in BufferedWriter.
         BufferedWriter buffWrite = new BufferedWriter(write);

         // The name of the file to open.
         String outputFile = "mathOutput.csv";

         while ((line = buffRead.readLine()) != null) {
            String[] value = line.split(",");
            operator[i] = value[1];
            number[i] = (Integer.parseInt(value[0])); // Change from a String to an integer.
            // Determine the operator and do the math operation and write to the output file.
            if (operator[i].equals("+")) { // if statement for addition operator
               total = total + number[i];
               buffWrite.write("Add  " + number[i] + "  total  " + total);
               buffWrite.newLine();
               if (operator[i].equals("-")) { // if statement for subtraction operator
                  total = total + number[i];
                  buffWrite.write("Subtract  " + number[i] + "  total  " + total);
                  buffWrite.newLine();
                  if (operator[i].equals("*")) { // if statement for multiplication operator
                     total = total + number[i];
                     buffWrite.write("Multiply  " + number[i] + "  total  " + total);
                     buffWrite.newLine();
                     if (operator[i].equals("/")) { // if statement for division operator
                        total = total + number[i];
                        buffWrite.write("Divide  " + number[i] + "  total  " + total);
                        buffWrite.newLine();
                        if (operator[i].equals("=")) { // if statement for equals operator
                           buffWrite.newLine();
                        }
                     }
                  }
               }
            }
         }
         // closing BufferedReader and BufferedWriter
         buffRead.close();
         buffWrite.close();
      }
      catch(FileNotFoundException ex) { // will catch if file is not found
         System.out.println( "Unable to open file '" + inputFile + "'");                                                
      }
      catch(IOException ex) // catches read and write errors
      {
         ex.printStackTrace(); // will print read or write error
      }
   }
}

Answer 1

1. String number[] 应为 int number[]。如果要对整数进行操作，请将各个变量的数据类型更改为 int。字符串不能用于数字相加。

2. 即使修复了上述异常，您也不会刷新写入操作。将数据写入文件需要 buffWrite.flush() 。在 bufWrite 上调用 close() 之前先调用 flush()。

编辑:存在许多逻辑错误，并且已得到解决。

import java.io.*;

public class CSVRead2 {
 public static void main(String args[]) {

  String operator[] = new String[1];
  int number[] = new int[1];
  int total = 0;
  int i=0;

  // The name of the file to open.
  String inputFile = "mathInput.csv";

  // This will reference one line at a time
  String line = null;

  try { // start monitoring code for Exceptions
     // FileReader reads text files in the default encoding.
     FileReader read = new FileReader("mathInput.csv");
     // Always wrap FileReader in BufferedReader.
     BufferedReader buffRead = new BufferedReader(read);

     // Assume default encoding.
     FileWriter write = new FileWriter("mathOuput.csv", true); // true for append
     // Always wrap FileWriter in BufferedWriter.
     BufferedWriter buffWrite = new BufferedWriter(write);

     // The name of the file to open.
     String outputFile = "mathOutput.csv";

     while ((line = buffRead.readLine()) != null) {
        String[] value = line.split(",");
        operator[i] = value[1];
        number[i] = (Integer.parseInt(value[0])); // Change from a String to an integer.
        // Determine the operator and do the math operation and write to the output file.
        if (operator[i].equals("+")) { // if statement for addition operator
           total = total + number[i];
           buffWrite.write("Add  " + number[i] + "  total  " + total);
           buffWrite.newLine();
        }else if (operator[i].equals("-")) { // if statement for subtraction operator
              total = total - number[i];
              buffWrite.write("Subtract  " + number[i] + "  total  " + total);
              buffWrite.newLine();
        }
        else if (operator[i].equals("*")) { // if statement for multiplication operator
                 total = total + number[i];
                 buffWrite.write("Multiply  " + number[i] + "  total  " + total);
                 buffWrite.newLine();
        }
        else if (operator[i].equals("/")) { // if statement for division operator
                    total = total + number[i];
                    buffWrite.write("Divide  " + number[i] + "  total  " + total);
                    buffWrite.newLine();
        }
        else if (operator[i].equals("=")) { // if statement for equals operator
                       buffWrite.newLine();
        }

    }
    buffWrite.flush();   
    // closing BufferedReader and BufferedWriter
    buffRead.close();
    buffWrite.close();
  }
  catch(FileNotFoundException ex) { // will catch if file is not found
     System.out.println( "Unable to open file '" + inputFile + "'");                                                
  }
  catch(IOException ex) // catches read and write errors
  {
     ex.printStackTrace(); // will print read or write error
  }
}
}

编辑2:

mathinput.csv(文件中没有空行)

2,+

3,+

9，-

数学输出.csv

添加2个共2个

添加3个，总共5个

总共减去9-4