錯誤，而試圖得到一筆錢

Question

我想獲得我的數組的總和稱爲矩陣。但是，當我編譯它時，我收到此錯誤：bad operand types for binary operator '+' first type: int; second type:int[]。我不明白爲什麼這會導致錯誤。請幫助我理解，這裏是我的代碼：

/** 
Sophia Ali 


1. Matrix, getSumMatrix, getSumMatrixDiag: 

    Email just Matrix.java. 

    Write a class called Matrix that contains a private 2-dimensional int 
    array called 'matrix' that can be up to 10 rows by 10 columns maximum. 
    Use two constants MAXROWS=10 and MAXCOLS=10 to construct 'matrix.' 

    The Matrix class will also need the following attributes: 

     private int rows; // number of rows to use in matrix 
     private int cols; // number of cols to use in matrix 

    The rows and cols will contains values that are less than equal to 
    MAXROWS and MAXCOLS. 


    Write a default Matrix class constructor that constructs the 'matrix' 
    array with the following values: 

     {{1,2,4,5},{6,7,8,9},{10,11,12,13}, {14,15,16,17}} 

    The constructor must also set the rows and cols variables to match the 
    above matrix. 


    Write a method 'getSumMatrix' that returns the sum of all the integers 
    in the array 'matrix'. 


    Write a method 'getSumMatrixDiag' that returns the sum of all the 
    integers in the major diagonal of the array 'matrix'. A major diagonal is 
    the diagonal formed from the top left corner to the bottom right corner of 
    the matrix. 


    You do not have to write a TestMatrix class to test the Matrix class. 
    Just use the BlueJ object creation and testing feature. 
*/ 
public class Matrix 
{ 

    static final int MAXROWS = 10; 
    static final int MAXCOLS = 10; 
    private int rows; 
    private int cols; 

    private int [][] matrix = new int [MAXROWS][MAXCOLS]; 

    public Matrix() 
    { 
    int matrix[][] = 
    { 
     {1, 2, 4, 5}, 
     {6, 7, 8, 9}, 
     {10, 11, 12, 13}, 
     {14, 15, 16, 17}}; 
     getSumMethod(matrix); 
     getSumMatrixDiag(matrix); 
    } 

    public int getSumMethod(int[][] matrix) 
    { 
     int sum = 0; 
     for (int i = 0; i < matrix.length; i++) { 
      sum += matrix[i]; 
     } 
     return sum; 
    } 

      /* 
     int i, result; 
     result = 0; 
     for(i=0; i < matrix.length; i++) 
     { 
      i++; 
      result = result + i; 
     } 
     return result; 
    } 
    */ 

    public int getSumMatrixDiag(int[][] matrix) 
    { 
     int sum = 0; 

     for (int i =0; i< matrix.length; i++) 
     { 
      i++; 
      sum = (int)(sum + matrix[i][i]); 
     } 
     return sum; 
     } 


     } 

Answer 1

當求和多維矩陣時，必須遍歷所有維度。所以在你的情況下你有一個二維數組，因此你需要兩個嵌套循環遍歷兩個數組。 你的循環：

int sum = 0; 
     for (int i = 0; i < matrix.length; i++) { 
      sum += matrix[i]; 
     } 
     return sum; 

應該像這樣：

int sum = 0; 
for(int i =0; i < matrix.length){ 
for(int j = 0; j < matrix[i].length; j++){ 
    sum += matrix[i][j]; 
} 
} 
return sum;