將輸出保存到文件

Question

我目前正在嘗試將通過我的對象創建的值放入文件中。 我的程序輸出工作正常，我在另一個類的方法中的計算工作。 我只想將matrixApp的輸出保存到文件中。 我還顯示了我的輸出看起來沒有嘗試保存到文件。 我采取的路線似乎沒有工作，有什么建議嗎？

import java.io.BufferedOutputStream;
import java.io.DataOutputStream;
import java.io.FileOutputStream;
import java.util.Scanner;


public class MatrixApp {

  public static void main(String[] args) {
    int m, n, p, q;

    Scanner input = new Scanner(System.in);
    System.out.println("Enter the number of rows and columns of first matrix");
    m = input.nextInt();
    n = input.nextInt();

    System.out.println("Enter the number of rows and columns of second matrix");
    p = input.nextInt();
    q = input.nextInt();

    System.out.println("Enter the elements of first matrix");

    int first[][] = new int[m][n];
    for (int c = 0; c < m; c++)
        for (int d = 0; d < n; d++)
            first[c][d] = input.nextInt();

    System.out.println("Enter the elements of second matrix");
    int second[][] = new int[p][q];

    for (int c = 0; c < p; c++)
        for (int d = 0; d < q; d++)
            second[c][d] = input.nextInt();



    MatrixMult matrixApp = new MatrixMult(first, second, m, n, p, q);

    //String filename = "data.txt";
    //FileOutputStream fout = new FileOutputStream(filename);
    //BufferedOutputStream bout = new BufferedOutputStream(fout);
    //DataOutputStream dout = new DataOutputStream(bout);
    //for (int i=0; i < matrixApp; i++){ <--- the problem is here and 
        //dout.writeInt(matrixApp[][]);   getting the program to do all the 
    //}                                   the outputs
  }
}

MatrixMult類

public class MatrixMult{

public MatrixMult(int first[][], int second[][], int m, int n, int p, int q) {
    doMatrixMultiply(first, second, m, n, p, q);
}

public void doMatrixMultiply(int first[][], int second[][], int m, int n, int p, int q) {

    if (n != p)
        System.out
                .println("Matrices with entered orders can't be multiplied with each other.");
    else {
        int multiply[][] = new int[m][q];
        int addition[][] = new int[m][q];
        int transpose[][] = new int[m][q];
        int transpose2[][] = new int[m][q];

        int mult = 0;
        int sum = 0;
        int tran = 0;


        for (int c = 0; c < m; c++) {
            for (int d = 0; d < q; d++) {
                for (int k = 0; k < p; k++) {
                    mult = mult + first[c][k] * second[k][d];
                }

                multiply[c][d] = mult;
                mult = 0;
            }
        }

        System.out.println("Product of entered matrices:-");

        for (int c = 0; c < m; c++) {
            for (int d = 0; d < q; d++)
                System.out.print(multiply[c][d] + "\t");

            System.out.print("\n");
        }

        for (int c = 0; c < m; c++) {
            for (int d = 0; d < q; d++) {
                for (int k = 0; k < p; k++) {
                    sum = first[c][d] + second[c][d];
                }

                addition[c][d] = sum;
                sum = 0;
            }
        }

        System.out.println("Sum of entered matrices:-");

        for (int c = 0; c < m; c++) {
            for (int d = 0; d < q; d++)
                System.out.print(addition[c][d] + "\t");

            System.out.print("\n");
        }

        int c;
        int d;
        for (c = 0; c < m; c++) {
            for (d = 0; d < q; d++)
                transpose[d][c] = first[c][d];
        }
        for (c = 0; c < m; c++) {
            for (d = 0; d < q; d++)
                transpose2[d][c] = second[c][d];
        }

        System.out.println("Transpose of first entered matrix:-");

        for (c = 0; c < n; c++) {
            for (d = 0; d < m; d++)
                System.out.print(transpose[c][d] + "\t");

            System.out.print("\n");
        }

        System.out.println("Transpose of second entered matrix:-");

        for (c = 0; c < n; c++) {
            for (d = 0; d < m; d++)
                System.out.print(transpose2[c][d] + "\t");

            System.out.print("\n");
        }
  }
}

matrixApp的輸出是

輸入矩陣的乘積： -

1 -2 -4
-1 7 -18

7 1 5
輸入矩陣的總和： -

4 0 -3
4 4 -5
2 -1 7
首次輸入矩陣的轉置： -

2 1 1
-1 0 1
0 -3 2
第二個輸入矩陣的轉置： -

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

Answer 1

你沒有關閉你的流 - 明確緩沖。 所以一切都在內存中，你永遠不會被沖到磁盤上。 使用try-with-resources語句適當地關閉所有內容，即使拋出異常：

try (FileOutputStream fout = new FileOutputStream(filename);
     BufferedOutputStream bout = new BufferedOutputStream(fout);
     DataOutputStream dout = new DataOutputStream(bout)) {
    // Note: Body here is as per original question. It won't compile, but
    // we don't know what was expected.
    for (int i=0; i < matrixApp; i++){
        dout.writeInt(matrixApp[][]);
    }
}

Answer 2

好像你想要保存一個名為matrixApp的MatrixMult對象。

為什么不序列化呢？

在MatrixMult實現java.io.Serializable ，然后調用dout.writeObject(matrixApp) 。

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編輯

根據您的評論，這里有一個關於如何序列化/反序列化的簡單示例 。

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如果你不想使用序列化，

我只想將matrixApp的輸出保存到文件中。

假設“輸出”是第first和second矩陣，

for (int i=0; i < first.length; i++){
    for(int j = 0; k < first[i].length; j++)
        dout.writeInt(first[i][j]);

for (int i=0; i < second.length; i++){
    for(int j = 0; k < second[i].length; j++)
        dout.writeInt(second[i][j]);

正如@JonSkeet解釋的那樣，將它與ressource一起try 。