Here you can find the source of base64Decode(String input)
public static byte[] base64Decode(String input)
//package com.java2s; /*/* w ww. j a v a 2 s.c o m*/ * This file is part of MML. * * MML is free software: you can redistribute it and/or modify * it under the terms of the GNU General Public License as published by * the Free Software Foundation, either version 2 of the License, or * (at your option) any later version. * * MML is distributed in the hope that it will be useful, * but WITHOUT ANY WARRANTY; without even the implied warranty of * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the * GNU General Public License for more details. * * You should have received a copy of the GNU General Public License * along with MML. If not, see <http://www.gnu.org/licenses/>. * (c) copyright Desmond Schmidt 2014 */ public class Main { private static final String codes = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/="; public static byte[] base64Decode(String input) { if (input.length() % 4 != 0) { throw new IllegalArgumentException("Invalid base64 input"); } byte decoded[] = new byte[((input.length() * 3) / 4) - (input.indexOf('=') > 0 ? (input.length() - input.indexOf('=')) : 0)]; char[] inChars = input.toCharArray(); int j = 0; int b[] = new int[4]; for (int i = 0; i < inChars.length; i += 4) { // This could be made faster (but more complicated) // by precomputing these index locations b[0] = codes.indexOf(inChars[i]); b[1] = codes.indexOf(inChars[i + 1]); b[2] = codes.indexOf(inChars[i + 2]); b[3] = codes.indexOf(inChars[i + 3]); decoded[j++] = (byte) ((b[0] << 2) | (b[1] >> 4)); if (b[2] < 64) { decoded[j++] = (byte) ((b[1] << 4) | (b[2] >> 2)); if (b[3] < 64) { decoded[j++] = (byte) ((b[2] << 6) | b[3]); } } } return decoded; } }