Print matrix to file 方法打印到文件

Question

在这个程序中，我尝试使用 java 打印编写器写入一个名为 m3 的输出文件。当 {{2,2,2},{2,2,2}} 的矩阵 f3 应生成输出文件时，以下输出的前两行保留用于行数和列数，如下所示f3 下的数组，输出文件应为 {{2},{3},{2,2,2},{2,2,2}}。我将问题隔离到主 try-catch 块中的 4 行代码。

import java.io.File;
import java.io.FileNotFoundException;
import java.io.PrintWriter;
import java.util.Scanner;


public class Test {
    
    /**
     * Error to output if can't open any files
     */
    public static final String ERR_FILE = "Error opening file(s)";
    
    /**
     * Error to output if files open but matrices
     * are of incompatible dimensions for multiplication
     */
    public static final String ERR_DIMS = "Bad matrix dimensions";
    
    private static void _outputMatrix(PrintWriter out, int[][] m, boolean includeDimensions) {      
        for (int r=0; r<m.length; r++) {
            if (includeDimensions && r==0) {
                out.printf("%d%n%d%n", m.length, m[0].length);
            }
            for (int c=0; c<m[r].length; c++) {
                out.printf("%d", m[r][c]);
                out.printf((c<m[r].length-1)?" ":"%n");
            }
        }
    }
    
    /**
     * Prints a matrix to the terminal
     * without dimensions
     * 
     * @param m matrix to print
     */
    public static void printMatrix(int[][] m) {
        _outputMatrix(new PrintWriter(System.out, true), m, false);
        
    }
    
    /**
     * Prints a matrix to a file
     * with associated dimensions
     * 
     * @param m matrix to print
     * @param pw open file
     */
    public static void printMatrix(int[][] m, PrintWriter pw) {
        _outputMatrix(pw, m, true);
    }
    
    /**
     * Checks if two matrices can be multiplied
     * (i.e. the columns of the first match
     * the rows of the second)
     * 
     * @param m1 matrix 1
     * @param m2 matrix 2
     * @return true if m1 x m2 is legal
     */
    public static boolean canMultiply(int[][] m1, int[][] m2) {
    
        
        int rows1 = m1.length;
        int rows2 = m2.length;
        
        if (rows1 == 0 || rows2 == 0) {
            return false;
        }
        
        int columns1 = m1[0].length;
   
        if (columns1 == rows2) {
            return true;
        }
        
        return false;
    }
    
    /**
     * Reads and returns a matrix from a scanner
     * Format:
     * m (# rows)
     * n (# #cols)
     * r0c0 r0c1 ... r0cn (values in row 0, column-by-column)
     * r1c0 r1c1 ... r1cn (values in row 1, column-by-column)
     * ...
     * rmc0 rmc1 ... rmcn (values in last row, column-by-column)
     * 
     * Results in...
     * int[][] {
     *  {r0c0, r0c1, ... r0cn},
     *  {r1c0, r1c1, ... r1cn},
     *  ...
     *  {rmc0, rmc1, ... rmcn}
     * }
     * 
     * @param s input source
     * @return resulting matrix
     */
    public static int[][] readMatrix(Scanner s) {
        int m = s.nextInt();
        int n = s.nextInt();
        int[][] matrix = new int[m][n];
        for (int i = 0; i < m; i++) {
            for (int j = 0; j < n; j++) {
                matrix[i][j] = s.nextInt();
            }
        }
        return matrix;
    }
    
    /**
     * Multiply two matrices and
     * return the result (assumes
     * input matrices are valid
     * for multiplication)
     * 
     * @param m1 matrix 1
     * @param m2 matrix 2
     * @return result of m1 x m2
     */
    public static int[][] matrixMultiply(int[][] m1, int[][] m2) {      
        int rows1 = m1.length;
        int columns1 = m1[0].length;
        int columns2 = m2[0].length;
     
        int[][] resultMatrix = new int[rows1][columns2];
        for (int i = 0; i < rows1; i++) {
            for (int j = 0; j < columns2; j++) {
                for (int k = 0; k < columns1; k++) {
                    resultMatrix[i][j] += (m1[i][k] * m2[k][j]);
                }
            }
        }
        return resultMatrix;
    }
    
    /**
     * Program to multiply matrices:
     * 1. Ask for paths for 3 files (2 input, 1 output)
     * 2. Check if inputs can be multiplied
     * 3. If so, multiply!
     *    - Output the full problem to the console
     *    - Output only the result matrix to the file
     * 
     * @param args command-line arguments, ignored
     */
    public static void main(String[] args) {
//      try(Scanner input = new Scanner(System.in)){
//          String m1, m2, m3;
//          
//          System.out.print("Enter path for matrix 1: ");
//          m1 = input.nextLine();
//          System.out.print("Enter path for matrix 2: ");
//          m2 = input.nextLine();
//          System.out.print("Enter path for result: ");
//          m3 = input.nextLine();
//          int[][] f1, f2, f3;
//           
//          Scanner file1 = new Scanner(new File(m1));
//          Scanner file2 = new Scanner(new File(m2));
//          PrintWriter output = new PrintWriter(new File(m3));
//  
//          
//          f1 = readMatrix(file1);
//          f2 = readMatrix(file2);
//          
//          
//          
//           
//          printMatrix(f1);
//          System.out.println("X");
//          printMatrix(f2);
//          System.out.println("=");
//          
//          if (canMultiply(f1, f2) != true) {
//              throw new Exception(ERR_DIMS);
//          }
//          
//          f3 = matrixMultiply(f1, f2);
//          
//          printMatrix(f3);
//          
//          printMatrix(f3, output);
//          
            
        
        try {
            int[][] f1 = {{2,2,2},{2,2,2}};
            PrintWriter output = new PrintWriter(new File("m3.txt"));
            printMatrix(f1);
            
            printMatrix(f1, output);
            
        } catch (FileNotFoundException e) {
            System.out.println(ERR_FILE);   
            
        } catch(Exception e) {
            System.out.println(e.getMessage());
        }
        
    }

}

我没有收到错误，而是没有任何内容被打印到 m3.txt 文件中。运行文件时不会抛出找不到文件，所以我的第一直觉是我初始化打印文件的方式有问题？