You are to write a program name matrix.java that multiply and add 2 matrices. 1.

Question

You are to write a program name matrix.java that multiply and add 2 matrices. 1. Your program should prompt the user for the dimensions of the two matrices, then check for compatibility (remember 2 matrices can be multiplied only if the column of the first is equal to the row of the second). You could prompt for ONE dimension and build two square matrices. Minimum dimension of matrix must be 25. 2. If the above is not met, prompt the user for new and compatible dimensions. 3. Now generate random integer numbers (ranging from 1 to 30) to fill both matrices. 4. Display these two matrices on the screen. 5. Multiply the two matrices and display the result on the screen. 6. Insert a clock to see how long it would take, in milliseconds, to multiply these two matrices and display the time (with a message to this effect). 7. Now add the two matrices and display the result on the screen. 8. Insert a clock to see how long it would take, in milliseconds, to add these two matrices and display the time (with a message to this effect). 9. Prompt the user asking if they want to repeat the program.

Explanation / Answer

import java.util.Scanner;
import java.util.Random;

class MatrixMultiplication
{
public static void main(String args[])
{
int m, n, p, q, sum = 0, c, d, k ;
Random r = new Random();

Scanner in = new Scanner(System.in);
System.out.println("*** Minimum dimension of Matrix must be 25 ***");
System.out.println("Enter the number of rows and columns of first matrix");
m = in.nextInt();
n = in.nextInt();
int Low = 0;
int High = 30;

int first[][] = new int[m][n];

for ( c = 0 ; c < m ; c++ )
for ( d = 0 ; d < n ; d++ )
first[c][d] = r.nextInt(High-Low) + Low;

System.out.println("Enter the number of rows and columns of second matrix");
p = in.nextInt();
q = in.nextInt();

if ( n != p )
System.out.println("Matrices with entered orders can't be multiplied with each other.");
else
{
int second[][] = new int[p][q];
int multiply[][] = new int[m][q];

for ( c = 0 ; c < p ; c++ )
for ( d = 0 ; d < q ; d++ )
second[c][d] = r.nextInt(High-Low) + Low;

long startTime = System.currentTimeMillis();

for ( c = 0 ; c < m ; c++ )
{
for ( d = 0 ; d < q ; d++ )
{
for ( k = 0 ; k < p ; k++ )
{
sum = sum + first[c][k]*second[k][d];
}

multiply[c][d] = sum;
sum = 0;
}
}
long elapsedTime = System.currentTimeMillis() - startTime;
System.out.println("Product of matrices: ");

for ( c = 0 ; c < m ; c++ )
{
for ( d = 0 ; d < q ; d++ )
System.out.print(multiply[c][d]+" ");

System.out.print(" ");
}

System.out.println("Time in ms elapsed for matrix mulitplication: " + elapsedTime);

if ( m != p && n !=q)
System.out.println("Matrices with entered orders can't be added with each other.");
else
{
int tot [][]= new int[m][n];
long start = System.nanoTime();
for ( c = 0 ; c < m ; c++ )
for ( d = 0 ; d < n ; d++ )
tot[c][d] = first[c][d] + second[c][d];

long elapsed = System.nanoTime() - start;

System.out.println("Sum of entered matrices:-");

for ( c = 0 ; c < m ; c++ )
{
for ( d = 0 ; d < n ; d++ )
System.out.print(tot[c][d]+" ");
System.out.println();
}
System.out.println("Time in ns elapsed for matrix addition: " + elapsed);

}
}
}

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