need a review for a finished code [closed]

Question

package homework2;

public class Homework2 {
    public static void main(String[] args){
    int num1 = (int) (Math.random()*(10-3+1)+3);
    int num2 = (int) (Math.random()*(10-3+1)+3);

    double[][] doubMatrix1 = new double[num1][num2];
    double[][] doubMatrix2 = new double[num1][num2];
    double[][] doubMatrix3 = new double[num1][num2];

    doubMatrix1 = getdoubMatrix(num1,num2);
    doubMatrix2 = getdoubMatrix(num1,num2);
    doubMatrix3 = addMatrices(doubMatrix1, doubMatrix2, num1, num2);        
    printDoubMatrix("First matrix", doubMatrix1);
    printDoubMatrix("Second matrix", doubMatrix2);
    printDoubMatrix("Result of adding", doubMatrix3);
    doubMatrix2 =transposeMatrix(num1,num2, doubMatrix2);
    printDoubMatrix("Second matrix transposed", doubMatrix2);
    doubMatrix3 = multipyMatrices(doubMatrix1, doubMatrix2);
    printDoubMatrix("Result of multiplying", doubMatrix3);




}

public static double[][] getdoubMatrix(int num1,int num2){

    double[][] tempArray = new double[num1][num2];
    for(int i = 0;i < tempArray.length;i++)
        for(int j = 0;j < tempArray[i].length;j++)
        {
            tempArray[i][j] = Math.random() * (100);                
        }
    return tempArray;
}

public static double[][] addMatrices(double[][] doubMatrix1, double[][] doubMatrix2,int d1,int d2)
{

    double[][] tempArray = null;
    if(doubMatrix1.length == doubMatrix2.length)
        if(doubMatrix1[0].length == doubMatrix2[0].length)
        {
             tempArray = new double[d1][d2];
            for(int i = 0; i< doubMatrix1.length;i++)
                  for(int j = 0; j< doubMatrix1[i].length;j++ )
                  {
                      tempArray[i][j] = doubMatrix1[i][j] + doubMatrix2[i][j];
                  }
        }
        else
        {
            return tempArray = new double[0][0];

        }

    return tempArray;
}

public static void printDoubMatrix(String text,double[][] doubMatrix1){

    System.out.println(text);
    for(int i = 0; i< doubMatrix1.length;i++)
    {
          for(int j = 0; j< doubMatrix1[i].length;j++ ) {                    
              System.out.printf("%9.1f", doubMatrix1[i][j]);                
          }
          System.out.println();
    }       
}

public static double[][] transposeMatrix(int num1, int num2, double[][] doubMatrix2){
    double[][] tempArray = new double[num2][num1];
    for(int i = 0;i < num1;i++)
        for(int j = 0;j < num2;j++)
        {
            tempArray[j][i] = doubMatrix2[i][j];               
        }    
    return tempArray;
}

public static double[][] multipyMatrices(double[][] doubMat1, double[][] doubMat2)

{                   
        double[][] tempArray = new double[doubMat1.length][doubMat2[0].length];
        if(doubMat1[0].length == doubMat2.length)
            if(doubMat1.length == doubMat2[0].length)
        {

                 for (int i = 0; i <doubMat1.length; i++)
                   {
                       for(int j = 0; j < doubMat2[0].length; j++)
                        {

                           for (int k = 0; k < doubMat2.length; k++)
                           {
                               tempArray[i][j] = tempArray[i][j] + doubMat1[i][k]*doubMat2[k][j];

                           }
                        }
                   }
        }
            else
            {

                return tempArray = new double[0][0];
            }
        return tempArray;
}

}

Hi, I've just finished this code, can some one review if this code is working correctly, please check if the transposed method and the multiplying method is working correctly and printing the right output.

thank you very much

this is my output

First matrix

 35.4     95.9     66.4     40.4     13.3     13.7
 10.9     18.7     92.3     30.0     57.2     68.5
 46.0     68.6     60.2     46.9     11.3     11.4
 87.7     82.0     15.8     82.6     93.2      8.2
 73.1     15.4     24.1     66.5     32.9     11.7
 19.8      8.4     13.2     63.4     63.5     73.9
 42.5     52.2     73.0      1.1     10.2     78.2
 56.2     40.6     55.9      3.6      9.3     12.9
 28.3      9.2      8.7     46.5     11.5     77.4

Second matrix

 30.1     78.6     44.7     12.5     31.8     83.5
 59.5      1.2     54.4     16.2     22.0     98.1
 24.0     25.7     92.2     92.9     90.9     95.9
  8.7     79.7      3.1     18.0     66.1      1.9
 89.7     85.1     74.7     89.5     27.8     27.4
 85.1     43.4     74.1     72.2     15.9     43.0
 71.2     23.1     41.3     72.5     78.8      1.1
 87.1     66.5     37.6     78.6     33.9     73.3
 48.4     70.5     43.6     22.5     35.7     13.2

Result of adding

 65.5    174.5    111.0     52.9     45.1     97.2
 70.4     19.9    146.7     46.2     79.2    166.6
 70.0     94.3    152.4    139.7    102.2    107.3
 96.4    161.8     18.9    100.6    159.4     10.0
162.8    100.5     98.8    156.0     60.7     39.0
104.9     51.8     87.2    135.6     79.4    116.9
113.7     75.3    114.3     73.6     89.0     79.3
143.3    107.1     93.5     82.3     43.1     86.2
 76.7     79.7     52.3     68.9     47.3     90.6

Second matrix transposed

 30.1     59.5     24.0      8.7     89.7     85.1     71.2     87.1     48.4
 78.6      1.2     25.7     79.7     85.1     43.4     23.1     66.5     70.5
 44.7     54.4     92.2      3.1     74.7     74.1     41.3     37.6     43.6
 12.5     16.2     92.9     18.0     89.5     72.2     72.5     78.6     22.5
 31.8     22.0     90.9     66.1     27.8     15.9     78.8     33.9     35.7
 83.5     98.1     95.9      1.9     27.4     43.0      1.1     73.3     13.2

Result of multiplying

 13644.0   8124.7  15701.1   9788.3  20645.5  15804.4  11466.2  16578.5  12927.1
 13839.9  14159.7  23804.4   6319.7  15612.6  14600.2  11773.1  14979.8   9492.2
 11370.3   8221.8  14886.3   7667.3  19284.5  15409.7  11648.3  15735.2  11295.1
  14484.4  10364.5  22593.6  15018.4  26241.1  20000.4  22139.9  23941.4  16011.0
   7349.0   8620.8  14654.6   5336.4  16859.7  14506.6  13984.9  15499.1   8499.9
  10832.3  11576.3  20651.2   6358.6  12938.4  11791.9  11826.7  15331.7   6794.0
  15516.4  14480.1  17621.0   5597.5  16226.0  14893.5   8214.2  16073.9  10339.5
   8798.8   7960.4   9956.4   4600.3  13605.0  11650.7   8254.8  11235.6   8599.1
  9379.3  10766.4  14501.3   2751.1  10572.3  10319.6   6950.2  13122.3   4877.7

Answer 1

First of all I would suggest to create class Matrix with the following structure:

class Matrix{

private double[][] data;

/* Creates a matrix with given two-dimension array */
public Matirx(double[][] data) { ... }

/* Creates a matrix with random numbers from given range */
public Matrix(double min, double max) { ... }

public Matrix transpose () { ... }

public Matrix add(Matrix second) { ... }

public Matrix multiply(Matrix second) { ... }

protected double[][] getData() { ... }

@Override
public String toString() { ... }

}

You can also add the private int fields for marix size and use it into transpose method instead of passing arguments.

Please, note that your Matrix class is immutable. Your methods should return a new matrices without changing the original ones.

Instead of printDoubMatrix() use toString() method.

After that in your main class just create two instances of Matrix classes and make use of them.