現在寫入文件的緩沖寫入器

Question

有人可以為我指出正確的方向，為什么它不寫入.txt文件？

這是我打印時得到的輸出。 我無法弄清楚代碼中的錯誤在哪里。 從輸出中可以看到。 它似乎在第一個循環中一切正常。 我的第一個問題是為什么它不將“ val 5”寫入.txt文件？ 我的第二個問題是，為什么在第二個矩陣之后它不再出現？

我是一名學生，很樂意對我的代碼提出任何反饋，以求更好。 請盡可能提出建議。

輸入：

1
5
3
3 -2 4
-1 5 2
-3 6 4

打印時輸出：

Size:1
insert 5
len: 1 
size2 1
val5 
Size:3 
insert 3
insert -2
insert 4
insert -1
insert 5
insert 2
insert -3
insert 6
insert 4
len: 9

.txt文件的輸出：

Matrix read: 
---------------------------------------

Matrix read: 
---------------------------------------

代碼如下：

import java.util.*;
import java.lang.*;
import java.io.*;

public class Driver{


public static void main(String[] args) {

  //initialize variables 
  String filepath;
  BufferedWriter bw = null;
  String toRead = "";
  CustomList[] arrayForList;
  CustomList listToBuild;



  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");

     //read user input
     Scanner user_input = new Scanner(System.in);
     filepath = user_input.next();

     //print out the file path for user to confirm the 
     //correct file path was entered
     System.out.println("Filepath read: " + filepath);
     System.out.println("");

     //finds the spot of the "." in .txt
     int extCounter = filepath.indexOf('.');
     String Output_Path = filepath.substring(0, extCounter);

     //close the scanner
     user_input.close();


     //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("_Output5_File.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();
     }

     //initialize array to hold strings
     String [] arrayToHoldInts = new String [100];


     //sets up filewriter to write output
     FileWriter fw = new FileWriter(file);
     bw = new BufferedWriter(fw);

     // open input stream test.txt for reading purpose.
     BufferedReader br = new BufferedReader(new FileReader(filepath));

     String input = "";
     input = br.readLine();
     int sizeOfArrayToStore = 0;
     while (input != null) {

        //below 2 lines get the size of the matrix
        sizeOfArrayToStore = Integer.parseInt(input);
        System.out.println("Size:" + sizeOfArrayToStore);

        //reads the next line after getting the size
        input = br.readLine();

        //checks for blanks and continues on error
        if (input.length() == 0){
           continue;
        }


        String [] stringSplitterForBR = null;
        arrayForList = new CustomList [sizeOfArrayToStore * sizeOfArrayToStore];

        //for loop to add ints parse the string that the
        //bufferred reader reads in. there is another nested
        //for loop to add each int that is parsed into a new
        //node for to build the list
        for (int i = 0; i < sizeOfArrayToStore; i++){
           listToBuild = new CustomList();
           stringSplitterForBR = input.split(" ");


           int tracker = 0;
           int valueToInsert = 0;   

           //for loop parses the ints and adds them into nodes
           //from the CustomList class
           for(int j = 0; j < sizeOfArrayToStore; j++) {
              valueToInsert = Integer.parseInt(stringSplitterForBR[tracker]);
              System.out.println("insert " + valueToInsert);
              listToBuild.addToList(valueToInsert);
              tracker++;
           }

           arrayForList[i] = listToBuild;
           input = br.readLine();

        }
        //Compute the deterimant using the same formula from 
        //Lab2


        int length = arrayForList.length;
        System.out.println("len: " + length);

        //print out the results to a .txt file


        bw.write("Matrix read: ");
        bw.newLine();
        bw.write("------------------" +
              "---------------------");
        bw.newLine();
        bw.flush();

        int size2 = 0;
        int valueToPrint;
        for (int x = 0; x < length; x++){

           listToBuild = arrayForList[x];
           size2 = listToBuild.sizeOfList();
           System.out.println("size2 " + size2);
           for (int y = 0; y < size2; y++) {

              valueToPrint = listToBuild.ValueOfNode(y);
              bw.write(valueToPrint);
              System.out.println("val" + valueToPrint);
              bw.flush();

           }
           bw.newLine();
        }


     }  
     bw.close();


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

 }
}

Answer 1

BufferedWriter上的write方法的語義與PrintStream上的println方法（ System.out是PrintStream ）的語義非常不同。 例如，您可以使用一個int值作為參數調用println ，並將其打印為數字，但是write方法將其解釋為單個字符的unicode，並且只會寫入單個字符-在您的代碼中，“ val 5”，即數字值為5的Unicode字符。

為您解決：更換BufferedWriter用PrintWriter和使用PrintWriter.println每當你想打印方法-它具有相同的語義println的方法System.out 。