How to multiply two matrices of different dimensions in Java

Problem Description:

How to multiply two matrices of different dimensions?

Solution:

Following example shows multiplication of two rectangular matrices with the help of two user defined methods multiply( int [] [] ,int [] []) and mprint(int [] []).

public class Matrix{
   public static int[][] multiply(int[][] m1, int[][] m2){
      int m1rows = m1.length;
      int m1cols = m1[0].length;
      int m2rows = m2.length;
      int m2cols = m2[0].length;
      if (m1cols != m2rows){
         throw new IllegalArgumentException("matrices 
         don't match: "+ m1cols + " != " + m2rows);
         int[][] result = new int[m1rows][m2cols];
         for (int i=0; i< m1rows; i++){
            for (int j=0; j< m2cols; j++){
               for (int k=0; k< m1cols; k++){
                  result[i][j] += m1[i][k] * m2[k][j];
                  return result;
               )
            }
         }
      }			
   }
/** Matrix print.
*/
   public static void mprint(int[][] a){
      int rows = a.length;
      int cols = a[0].length;
      System.out.println("array["+rows+"]["+cols+"] = {");
      for (int i=0; i< rows; i++){
         System.out.print("{");
         for (int j=0; j< cols; j++){
            System.out.print(" " + a[i][j] + ",");
            System.out.println("},");
         }
      }
      System.out.println(":;");
   }
   public static void main(String[] argv){
      int x[][] ={
      { 3, 2, 3 },
      { 5, 9, 8 },
      };

      int y[][] ={
      { 4, 7 },
      { 9, 3 },
      { 8, 1 },
      };

      int z[][] = Matrix.multiply(x, y);
      Matrix.mprint(x);
      Matrix.mprint(y);
      Matrix.mprint(z);
   }
}

Result:

The above code sample will produce the following result.

array[2][3]={
{3, 2, 3}
 {5, 9, 8}
};

array[3][2]={
{4, 7}
{9, 3}
{8, 1}
};

array[2][2]={
{63, 30}
{165, 70}
};