算法提高 矩阵相乘

import java.io.BufferedInputStream;
import java.math.BigInteger;
import java.util.Scanner;

public class Main {

    public static BigInteger[][] Mul(BigInteger[][] A ,int col1,BigInteger[][] B,int col2){
        BigInteger[][] C = new BigInteger[A.length][col2];
        for ( int i = 0 ; i < A.length ; i++){
            for ( int k = 0 ; k < col2 ; k++){
                BigInteger sum = BigInteger.ZERO;
                for ( int j = 0 ; j < col1 ; j++){
                    sum = sum.add(A[i][j].multiply(B[j][k]));
                }
                C[i][k] = sum; 
            }
        }
        return C;
    }

    public static void main(String[] args) {
        // TODO Auto-generated method stub
        Scanner in = new Scanner(new BufferedInputStream(System.in));
        int i,j,m,n;
        i = in.nextInt();
        j = in.nextInt();
        BigInteger[][] A = new BigInteger[i][j];
        for ( int a = 0 ; a < i ; a++){
            for ( int b = 0 ; b < j ; b++){
                A[a][b] = new BigInteger(in.next());
            }
        }
        m = in.nextInt();
        n = in.nextInt();
        BigInteger[][] B = new BigInteger[m][n];
        for ( int a = 0 ; a < m ; a++){
            for ( int b = 0 ; b < n ; b++){
                B[a][b] = new BigInteger(in.next());
            }
        }
        BigInteger[][] C = Mul(A, j, B, n);
        for ( int p = 0 ; p < C.length ; p++){
            System.out.print(C[p][0]);
            for ( int q = 1 ; q < n ; q++){
                System.out.print(" "+C[p][q]);
            }
            System.out.println();
        }
        in.close();
    }

}