Q7

Question 7

Question - 8 Write java program for the following matrix operations:

**a. Addition of two matrices

b. Multiplication of two matrices

c. Transpose of a matrix -- Take input of elements of matrices from user

Code Insights

Created java_2.java, a new java class file and imported java.util.Scanner package to take user input, defined all array and integer variables to store values, method printMatrix takes input of array of integers, its rows and columns and just displays/prints to terminal in desired matrix manner.

In the main method Scanner class object takes the desired input of rows and columns for the two matrices on which the operations will be performed, then takes matrix value inputs (all elements in one-line separated by space " ".).

For Addition: Used nested for-loops to get sum of each indexed value of matrix (array).

For Multiplication: Checks if multiplication is possible for the two matrices and then uses nested for loops to do matrix multiplication corresponding row-wise and column-wise.

For Transposition: Uses two nested for loops to go through each element and swap row and column indexes to transpose the given matrix.

Possible Error Handling

• In Matrix addition two matrices need to be of same size,

• In Matrix multiplication columns of matrix one should equal to rows of matrix two,

• No exceptions for transpose it is possible for all matrices.

Browse Source Code

Code

/**
 *Solution for Ans. 7
 * @author Jatin Kamboj 8647
 */
import java.util.Scanner;

public class java_2 {
    public static void main(String[] args) {

        System.out.print("\n\tThis program will take"
                + "two arrays as inputs and will perform "
                + "Matrix { addition, multiplication,"
                + " transposition }.\n"
                + "Please enter desired input parameters "
                + "that would make all the operations "
                + "possible (addition and multiplication "
                + "- rows and columns values). \n");
        int row_1, col_1, row_2, col_2;
        Scanner s = new Scanner(System.in);
        System.out.print("\nEnter number of rows "
                + "for the first matrix: ");
        row_1 = s.nextInt();
        System.out.print("Enter number of columns "
                + "for the first matrix: ");
        col_1 = s.nextInt();
        System.out.print("\nEnter number of rows "
                + "for the second matrix: ");
        row_2 = s.nextInt();
        System.out.print("Enter number of columns "
                + "for the second matrix: ");
        col_2 = s.nextInt();
        if (row_1 == row_2 && col_1 == col_2) {
            int[][] first_array = new int[row_1][col_1];
            int[][] second_array = new int[row_2][col_2];
            int[][] sum = new int[row_2][col_2];
            int[][] prod = new int[row_2][col_2];
            int[][] trans1 = new int[row_1][col_1];
            int[][] trans2 = new int[row_2][col_2];

            System.out.println("\nEnter all the elements "
                    + "of first matrix row-wise: ");
            for (int i = 0; i < row_1; i++) {
                for (int j = 0; j < col_1; j++) {
                    first_array[i][j] = s.nextInt();
                }
            }
            System.out.println("\nEnter all the elements "
                    + "of second matrix row-wise: ");
            for (int i = 0; i < row_2; i++) {
                for (int j = 0; j < col_2; j++) {
                    second_array[i][j] = s.nextInt();
                }
            }
            System.out.print("\nFirst Matrix: \n");
            printMatrix(row_1, col_1, first_array);
            System.out.println("\nSecond Matrix: ");
            printMatrix(row_2, col_2, second_array);
            System.out.println("\nMatrix after addition: ");
            for (int i = 0; i < row_1; i++) {
                for (int j = 0; j < col_2; j++) {
                    for (int k = 0; k < col_1; k++) {
                        sum[i][j] = first_array[i][j]
                                  + second_array[i][j];
                    }
                }
            }
            printMatrix(row_2, col_2, sum);
            System.out.println("\nMatrix after" +
                    " Multiplication: ");
            // Check if multiplication is Possible
            if (row_2 != col_1) {
                System.out.println("\nMultiplication" +
                        " Not Possible");
            }
            // Multiply the two matrices
            for (int i = 0; i < row_1; i++) {
                for (int j = 0; j < col_2; j++) {
                    for (int k = 0; k < row_2; k++) {
                        prod[i][j] += first_array[i][k] 
                                    * second_array[k][j];
                    }
                }
            }
            printMatrix(row_2, col_2, prod);
            System.out.println("\nFirst Matrix After" +
                    " Transpose: ");
            for (int i = 0; i < row_2; i++) {
                for (int j = 0; j < col_2; j++) {
                    trans1[i][j] = first_array[j][i];
                }
            }
            printMatrix(row_1, col_1, trans1);
            System.out.println("\nSecond Matrix" +
                    " After Transpose: ");
            for (int i = 0; i < row_2; i++) {
                for (int j = 0; j < col_2; j++) {
                    trans2[i][j] = second_array[j][i];
                }
            }
            printMatrix(row_1, col_1, trans2);
        } else {
            System.out.println("\nOperation would not "
                    + "be possible for the given input");
        }

    }

    private static void printMatrix(
            int rows, 
            int cols, 
            int[][] array_of_matrix) {
        StringBuilder str = new StringBuilder("[ ");
        for (int i = 0; i < rows; i++) {
            for (int j = 0; j < cols; j++) {
                str.append(array_of_matrix[i][j]).append(" ");
            }

            System.out.println(str + "]");
            str = new StringBuilder("[ ");
        }
    }
}

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