Here you can find the source of multiplyMatrixByMatrix(double[][] a, double[][] b)
public static double[][] multiplyMatrixByMatrix(double[][] a, double[][] b) throws IllegalArgumentException
//package com.java2s; /******************************************************************************* * Copyright 2010 Simon Mieth//from w ww. j a v a 2s.c o m * * Licensed under the Apache License, Version 2.0 (the "License"); * you may not use this file except in compliance with the License. * You may obtain a copy of the License at * * http://www.apache.org/licenses/LICENSE-2.0 * * Unless required by applicable law or agreed to in writing, software * distributed under the License is distributed on an "AS IS" BASIS, * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. * See the License for the specific language governing permissions and * limitations under the License. ******************************************************************************/ public class Main { public static double[][] multiplyMatrixByMatrix(double[][] a, double[][] b) throws IllegalArgumentException { if (a[0].length != b.length) { throw new IllegalArgumentException("Cannot multiply a with b, columns of a != rows of b. "); } double[][] c = new double[a.length][b[0].length]; for (int i = 0; i < a.length; i++) { for (int x = 0; x < b.length; x++) { for (int y = 0; y < a[i].length; y++) { c[i][x] += (a[i][y] * b[y][x]); } } } return c; } }