Matrix multiplication

import java.util.Arrays;
import java.util.Scanner;
public class Matrix {

    private static int counter =0;
    private static Scanner scanner = new Scanner(System.in);
    private int rawForArr1 , columnforarr1Andrawsforarr2, columnForArr2 =0; //

    public Matrix(){
    }


    public Matrix(int rawForArr1, int columnforarr1Andrawsforarr2, int columnForArr2) {
        this.rawForArr1 = rawForArr1;
        this.columnforarr1Andrawsforarr2 = columnforarr1Andrawsforarr2;
        this.columnForArr2 = columnForArr2;
    }

    public void setRawsAndColumn(){
        setRawsAndColumns();
    }

    private void setRawsAndColumns(){
        System.out.println("Enter numbers of raws for the (LEFT ARRAY)");
        int r1=scanner.nextInt();
        this.rawForArr1 =r1;
        System.out.println("\nEnter numbers of columns for the (LEFT ARRAY).\nThis value automatically will be assigned for the raws in the right matrix ensuring 'Valid Multiplication'\n");
        int colArr1RawArr2 = scanner.nextInt();
        this.columnforarr1Andrawsforarr2 =colArr1RawArr2;
        System.out.println("Enter numbers of columns for the (RIGHT ARRAY)");
        int c2=scanner.nextInt();
        this.columnForArr2 = c2;
        double [][] firstArr = new double[r1][colArr1RawArr2];
        double [][] secondArr = new double[colArr1RawArr2][c2];
        enterElements(firstArr);
        enterElements(secondArr);
        double[][] multiplied =multiplieMatrix(firstArr,secondArr);
        printValue(multiplied);
    }


    // Print the Matrix as a string of Array
    public static void printValue(double[][] arr)
    {
                System.out.println(Arrays.deepToString(arr));
    }

    public static double [][] multiplieMatrix(double [][] leftArr,double[][] rightArr){
        int m = leftArr.length;
        int n = rightArr[0].length;
        double [][] sumOfMultiplie = new double[m][n];
        int lARawIndex =0,rACIndex=0,iterateOnLArrColAndRArrRaw=0;
        double sum = 0 ;
        for(lARawIndex =0 ; lARawIndex < leftArr.length ; ++lARawIndex)
        {
            for(rACIndex = 0 ; rACIndex < rightArr[0].length ; ++rACIndex)
            {
                for(iterateOnLArrColAndRArrRaw = 0 ; iterateOnLArrColAndRArrRaw < rightArr.length ; ++iterateOnLArrColAndRArrRaw)
                {
                    sum+= (leftArr[lARawIndex][iterateOnLArrColAndRArrRaw]) * (rightArr[iterateOnLArrColAndRArrRaw][rACIndex]);
                }
                sumOfMultiplie[lARawIndex][rACIndex]=sum ;
                sum=0;
            }
        }
        return sumOfMultiplie ;
    }
    /* enter elements of the array*/
    public static double[][] enterElements(double[][] arr)
    {
        counter++;
        if(counter%2==0){
            System.out.println("\t***(Enter the elements for the RIGHT array)***\n");
        }
        System.out.println("\t ***(Enter the elements for the LEFT array)***\n");
        for(int i = 0 ; i < arr.length ; ++i) // numbers of raws
        {
            for(int j = 0 ; j<arr[0].length ; ++j) // numbers of columns
            {
                System.out.println("Enter element in raw #"+(i+1)+" column #"+(j+1));
                arr[i][j] = scanner.nextDouble();
            }
        }
        return arr ;

    }

//
//    public static  double[][] recursiveMultiplicationMatrix(double [][] multilplies ){
//        double[][] nextMatrix =initilizeMatrix();
//        enterElements(nextMatrix);
//        int m = nextMatrix.length;
//        int n = multilplies[0].length;
//        double [][] sumOfMultiplie = new double[m][n];
//        int lARawIndex =0,rACIndex=0,iterateOnLArrColAndRArrRaw=0;
//        int sum = 0 ;
//        for(lARawIndex =0 ; lARawIndex < nextMatrix.length ; ++lARawIndex)
//        {
//            for(rACIndex = 0 ; rACIndex < multilplies[0].length ; ++rACIndex)
//            {
//                for(iterateOnLArrColAndRArrRaw = 0 ; iterateOnLArrColAndRArrRaw < multilplies.length ; ++iterateOnLArrColAndRArrRaw)
//                {
//                    sum+= (nextMatrix[lARawIndex][iterateOnLArrColAndRArrRaw]) * (multilplies[iterateOnLArrColAndRArrRaw][rACIndex]);
//                }
//                sumOfMultiplie[lARawIndex][rACIndex]=sum ;
//                sum=0;
//            }
//        }
//
//            String answer = answer();
//            if (answer.equals("yes")) {
//                return recursiveMultiplicationMatrix(sumOfMultiplie);
//
//            }
//        return sumOfMultiplie ;
//
//    }
//
//    public static String answer(){
//        System.out.println("Do you want to continue to multiple? "+'\n'+"enter yes to continue or any other key to print the 2d matrix");
//        String answer ;
//        answer = scanner.nextLine();
//        return answer;
//    }



}

Python matrix multiplication

>>> a = np.array([[ 5, 1 ,3], 
                  [ 1, 1 ,1], 
                  [ 1, 2 ,1]])
>>> b = np.array([1, 2, 3])
>>> print a.dot(b)
array([16, 6, 8])

-1

Source: stackoverflow.com

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