Question

Write a method to multiply two matrices. The header of the method is: public static double[][] multiplyMatrix(double[][] a, double[][] b) To multiply matrix a by matrix b, the number of columns in a must be the same as the number of rows in b, and the two matrices must have elements of the same or compatible types. Let c be the result of the multiplication. Assume the column size of matrix a is n. Each element is For example, for two matrices a and b, c is where Write a test program that prompts the user to enter two matrices and displays their product. Write in java language, with comments and display a flowchart.

Answer 1

Hey,

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import java.util.Scanner;
public class MultiplyMatrixTest {

public static double[][] multiplyMatrix(double[][] a, double[][] b) {
double[][] result = new double[a.length][b[0].length];
for(int i = 0; i < result.length; ++i) {
for(int j = 0; j < result[i].length; ++j) {
double total = 0;
for(int k = 0; k < a[i].length; ++k) {
total += (a[i][k] * b[k][j]);
}
result[i][j] = total;
}
}
return result;
}

public static void main(String[] args) {
Scanner sc=new Scanner(System.in);
double[][] matrix1;
double[][] matrix2;
int m1,n1,m2,n2;
System.out.println("Enter number of rows for matrix 1: ");
m1=sc.nextInt();
System.out.println("Enter number of columns for matrix 1: ");
n1=sc.nextInt();
matrix1=new double[m1][n1];
for(int i = 0; i < m1; ++i) {
for(int j = 0; j < n1; ++j) {
System.out.println("Enter element at index ("+i+", "+j+")");
matrix1[i][j]=sc.nextDouble();
  
}
}

System.out.println("Enter number of rows for matrix 2: ");
m2=sc.nextInt();
System.out.println("Enter number of columns for matrix 2: ");
n2=sc.nextInt();
  
matrix2=new double[m2][n2];
for(int i = 0; i < m2; ++i) {
for(int j = 0; j < n2; ++j) {
System.out.println("Enter element at index ("+i+", "+j+")");
matrix2[i][j]=sc.nextDouble();
  
}
}
if(n1!=m2)
{
System.out.println("Error!!");
return;
}
double[][] result = multiplyMatrix(matrix1, matrix2);

for(int i = 0; i < result.length; ++i) {
for(int j = 0; j < result[i].length; ++j) {
System.out.print(result[i][j] + " ");
}
System.out.println();
}
}

}

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