Question

以下代码适用于我一直在进行的项目。输出必须是.txt文件。当while循环运行多次时，我无法让缓冲的写入器写入。我已经尝试过故障排除和测试，但是无法让它工作。如果我做system.out.prints，输出是正确的，所以我认为问题在于缓冲的编写器。我目前没有bw.close（），但我已经尝试将它放在多个位置，但它仍然无效。 bw.write（＆＃34;你好＆＃34;）只是我试图解决问题。我的bw.flush（）是否在错误的位置？

我的第二个问题是，这是将输出写入.txt文件的最佳方法吗？我对新方式持开放态度，并希望得到一些建议，以帮助拓宽我对java的了解。

public class Driver{


public static void main(String[] args) {

  String filepath;
  BufferedWriter bw = null;

  // TODO Auto-generated method stub
  try {
     System.out.println("To find the determinant of a Matrix, please enter the file below!");
     System.out.println("Please enter the file path of the txt file:\n");


     Scanner user_input = new Scanner(System.in);
     filepath = user_input.next();

     System.out.println("Filepath read: " + filepath);
     System.out.println("");
     int extCounter = filepath.indexOf('.');
     String Output_Path = filepath.substring(0, extCounter);

     // Read input file
     Scanner input = new Scanner(new File(filepath));

     //while loop to read in the text file
     while (input.hasNextInt()) {

        //find the size given by the first int
        //size is then used to allocate the array
        //to the correct size
        int size = input.nextInt();
        int[][] a = new int[size][size];

        for (int i = 0; i < size; i++) {
           for (int j = 0; j < size; j++) {

              try{
                 a[i][j] = input.nextInt();

              }
              catch (java.util.NoSuchElementException e) {
                 e.printStackTrace();
              }
           }
        }

        //Specify the file name and path here
        //the below code allows the user to enter one path
        //and get the output file at the same path
        //without having to enter it twice
        String OutFile;
        OutFile = Output_Path.concat("_Output_File15.txt");
        File file = new File(OutFile);

        /* This logic will make sure that the file 
         * gets created if it is not present at the
         * specified location*/
        if (!file.exists()) {
           file.createNewFile();
        }

        FileWriter fw = new FileWriter(file);
        bw = new BufferedWriter(fw);


        //print out the determinant by
        //calling the determinant method
        Deter deterMethod = new Deter();
        bw.write("The Determinant is: "
              + deterMethod.determinant(a) + " ...");
        int deterInt = deterMethod.determinant(a);
        System.out.println(deterInt);
        bw.write("" + deterInt);
        bw.write("hello");
        bw.write(deterInt);
        bw.flush();
        //deterInt = 0;
        //print a blank line 
        System.out.println();

     }
  } catch (Exception e) {
     e.printStackTrace();
  }
}





//determinant method
public class Deter
{
public static int determinant(int matrix [][]) { 

  //initializes the sum at 0
  int sum = 0;

  //base case 
  //1 x 1 matrix (x) is det(a) = x
  if (matrix.length == 1) {
     return matrix[0][0]; 

  } else {

     //for loop to cycle through the columns
     for (int j = 0; j < matrix.length; j++) {

        //equation to figure out the minor of the array given.
        //Deletes a row and column as provided by the definition
        //of a minor
        int[][] minor = new int[matrix.length - 1]
              [matrix.length - 1];

        //for loop to cycle through the rows
        for (int row = 1; row < matrix.length; row++) {
           for (int column = 0; 
                 column < matrix.length; column++) {


              if (column < j) { 
                 minor[row - 1][column] = matrix[row][column];
              } else if (column > j) {
                 minor[row - 1][column - 1] = matrix[row][column];
              }
           }
        }

        //recursive equation to get the 
        //sum to find the determinent 
        sum+=matrix[0][j]*Math.pow(-1,j)*determinant(minor);
     }
  }
  //return the sum to be printed out
  return sum;
} 
}

Answer 1

当你在循环的每次迭代中创建一个新的FileWriter时，文件将被覆盖，因此要么在循环之前移动FileWriter的创建或使用指示追加的构造函数

https://docs.oracle.com/javase/7/docs/api/java/io/FileWriter.html#FileWriter(java.io.File,%20boolean)

尝试通过创建更多方法来模块化代码

E，G，

 private Scanner getFileScanner () {

 Scanner user_input = new Scanner(System.in);
 String filepath = user_input.next();

 System.out.println("Filepath read: " + filepath);
 // Read input file
 Scanner input = new Scanner(new File(filepath));
 return input
}

缓冲的Writer写.txt文件

1 个答案: