java执行数组计算

Question

下面的代码将打印两个方阵，我需要它们在两个矩阵之间执行乘法，但我似乎无法让该部分工作。我在问题所在的代码块之前添加了注释。但目前它打印的只是零。我在网上浏览了很多网站，但似乎无法让我的网站工作。

 import java.util.*;
    import java.math.*;

    public class Main {

    public static void main(String[] args) {

        //create the grid
        final int rowWidth = 9;
        final int colHeight = 9;

        Random rand = new Random();

        int [][] board = new int [rowWidth][colHeight];

        //fill the grid
        for (int row = 0; row < board.length; row++) {

            for (int col = 0; col < board[row].length; col++) {

                board[row][col] = rand.nextInt(10);
            }
        }

        //display output
        for(int i = 0; i < board.length; i++) {

            for(int j = 0; j < board[i].length; j++) {

                System.out.print(board[i][j] + " ");
                //System.out.println();
            }
            System.out.println();
        }

                System.out.println();


                int [][] board2 = new int [rowWidth][colHeight];

        //fill the grid
        for (int row2 = 0; row2 < board2.length; row2++) {

            for (int col2 = 0; col2 < board[row2].length; col2++) {

                board[row2][col2] = rand.nextInt(10);
            }
        }

        //display output
        for(int m = 0; m < board2.length; m++) {

            for(int n = 0; n < board[m].length; n++) {

                System.out.print(board[m][n] + " ");

            }
            System.out.println();
        }

    //error is somewhere here

          int[][] calculationMultiplication = new int[rowWidth][colHeight];
      for (int l = 0; l < rowWidth; l++) {
          for (int t = 0; t < colHeight; t++) {
              for (int z = 0; z < rowWidth; z++) {
                calculationMultiplication[l][t] = calculationMultiplication[l][t] + board[l][z] * board2[z][t];
              }
          }
      }    

    //display output

      System.out.println("\nProduct of the 2 matrices is ");
      for (int i = 0; i < calculationMultiplication.length; i++) {
          for (int j = 0; j < calculationMultiplication[0].length; j++) {
              System.out.print(calculationMultiplication[i][j] + " ");
          }
          System.out.println();
      }

    } //end of main
    } //end of class Main

Answer 1

问题是您尚未填充 board2 数组，因此它的所有元素都将为 0。在 for 循环中，您还应该为 board2 分配随机值。您对 board 数组执行了两次。

//fill the grid
for (int row2 = 0; row2 < board2.length; row2++) {
    for (int col2 = 0; col2 < board2[row2].length; col2++) { // notice 'board2[row].length'
        board2[row2][col2] = rand.nextInt(10);
    }
}

您应该在显示数组的 for 循环中执行类似的操作:

//display output
for (int m = 0; m < board2.length; m++) {
    for (int n = 0; n < board2[m].length; n++) { // notice 'board2[row].length'
        System.out.print(board2[m][n] + " ");
    }
    System.out.println();
}