Hex（十六进制）和Base64类似，并不是一种加密算法，而是一种编码的手段，重新编码之后的数据很容易还原，用于加密的话，只防君子而不防小人
这两种编码方式可以将byte数组转化为方便查看的字符串
比如使用MD5对字符串加密：
public static void main(String[] args) throws Exception { System.out.println(new String(DigestUtils.md5("啊哈iuashuai"))); }
控制台显示：
�X�L����={�=b ��
虽然这一堆的字符串可以解密还原，但是并不方便保存，如果使用16进制进行编码：
public static void main(String[] args) throws Exception { System.out.println(Hex.encodeToString(DigestUtils.md5("啊哈iuashuai"))); }
控制台显示：
ab58f24ccbcecaef3d7bb73d621ffba5
进行16进制编码之后的数据就十分方便保存，可以读出来，告诉别人，存在数据库中，也方便查看。
16进制编码
代码选自Common-codec
public class Hex { public static String encodeToString(byte bytes[]) { char encodedChars[] = encode(bytes); return new String(encodedChars); } public static char[] encode(byte data[]) { int l = data.length; char out[] = new char[l << 1]; int i = 0; int j = 0; for (; i < l; i++) { out[j++] = DIGITS[(240 & data[i]) >>> 4]; out[j++] = DIGITS[15 & data[i]]; } return out; } public static byte[] decode(String hex) { return decode(hex.toCharArray()); } public static byte[] decode(char data[]) throws IllegalArgumentException { int len = data.length; if ((len & 1) != 0) throw new IllegalArgumentException("Odd number of characters."); byte out[] = new byte[len >> 1]; int i = 0; for (int j = 0; j < len;) { int f = toDigit(data[j], j) << 4; j++; f |= toDigit(data[j], j); j++; out[i] = (byte) (f & 255); i++; } return out; } protected static int toDigit(char ch, int index) throws IllegalArgumentException { int digit = Character.digit(ch, 16); if (digit == -1) throw new IllegalArgumentException((new StringBuilder()).append("Illegal hexadecimal charcter ").append(ch) .append(" at index ").append(index).toString()); else return digit; } private static final char DIGITS[] = { '0', '1', '2', '3', '4', '5', '6', '7', '8', '9', 'a', 'b', 'c', 'd', 'e', 'f' }; }
Base64编码
代码选自阿里巴巴Druid.jar
public class Base64 { public Base64() { } public static String byteArrayToBase64(byte a[]) { return byteArrayToBase64(a, false); } public static String byteArrayToAltBase64(byte a[]) { return byteArrayToBase64(a, true); } private static String byteArrayToBase64(byte a[], boolean alternate) { int aLen = a.length; int numFullGroups = aLen / 3; int numBytesInPartialGroup = aLen - 3 * numFullGroups; int resultLen = 4 * ((aLen + 2) / 3); StringBuilder result = new StringBuilder(resultLen); char intToAlpha[] = alternate ? intToAltBase64 : intToBase64; int inCursor = 0; for (int i = 0; i < numFullGroups; i++) { int byte0 = a[inCursor++] & 255; int byte1 = a[inCursor++] & 255; int byte2 = a[inCursor++] & 255; result.append(intToAlpha[byte0 >> 2]); result.append(intToAlpha[byte0 << 4 & 63 | byte1 >> 4]); result.append(intToAlpha[byte1 << 2 & 63 | byte2 >> 6]); result.append(intToAlpha[byte2 & 63]); } if (numBytesInPartialGroup != 0) { int byte0 = a[inCursor++] & 255; result.append(intToAlpha[byte0 >> 2]); if (numBytesInPartialGroup == 1) { result.append(intToAlpha[byte0 << 4 & 63]); result.append("=="); } else { int byte1 = a[inCursor++] & 255; result.append(intToAlpha[byte0 << 4 & 63 | byte1 >> 4]); result.append(intToAlpha[byte1 << 2 & 63]); result.append('='); } } return result.toString(); } public static byte[] base64ToByteArray(String s) { return base64ToByteArray(s, false); } public static byte[] altBase64ToByteArray(String s) { return base64ToByteArray(s, true); } private static byte[] base64ToByteArray(String s, boolean alternate) { byte alphaToInt[] = alternate ? altBase64ToInt : base64ToInt; int sLen = s.length(); int numGroups = sLen / 4; if (4 * numGroups != sLen) throw new IllegalArgumentException("String length must be a multiple of four."); int missingBytesInLastGroup = 0; int numFullGroups = numGroups; if (sLen != 0) { if (s.charAt(sLen - 1) == '=') { missingBytesInLastGroup++; numFullGroups--; } if (s.charAt(sLen - 2) == '=') missingBytesInLastGroup++; } byte result[] = new byte[3 * numGroups - missingBytesInLastGroup]; int inCursor = 0; int outCursor = 0; for (int i = 0; i < numFullGroups; i++) { int ch0 = base64toInt(s.charAt(inCursor++), alphaToInt); int ch1 = base64toInt(s.charAt(inCursor++), alphaToInt); int ch2 = base64toInt(s.charAt(inCursor++), alphaToInt); int ch3 = base64toInt(s.charAt(inCursor++), alphaToInt); result[outCursor++] = (byte) (ch0 << 2 | ch1 >> 4); result[outCursor++] = (byte) (ch1 << 4 | ch2 >> 2); result[outCursor++] = (byte) (ch2 << 6 | ch3); } if (missingBytesInLastGroup != 0) { int ch0 = base64toInt(s.charAt(inCursor++), alphaToInt); int ch1 = base64toInt(s.charAt(inCursor++), alphaToInt); result[outCursor++] = (byte) (ch0 << 2 | ch1 >> 4); if (missingBytesInLastGroup == 1) { int ch2 = base64toInt(s.charAt(inCursor++), alphaToInt); result[outCursor++] = (byte) (ch1 << 4 | ch2 >> 2); } } return result; } private static int base64toInt(char c, byte alphaToInt[]) { int result = alphaToInt[c]; if (result < 0) throw new IllegalArgumentException((new StringBuilder()).append("Illegal character ").append(c).toString()); else return result; } private static final char intToBase64[] = { 'A', 'B', 'C', 'D', 'E', 'F', 'G', 'H', 'I', 'J', 'K', 'L', 'M', 'N', 'O', 'P', 'Q', 'R', 'S', 'T', 'U', 'V', 'W', 'X', 'Y', 'Z', 'a', 'b', 'c', 'd', 'e', 'f', 'g', 'h', 'i', 'j', 'k', 'l', 'm', 'n', 'o', 'p', 'q', 'r', 's', 't', 'u', 'v', 'w', 'x', 'y', 'z', '0', '1', '2', '3', '4', '5', '6', '7', '8', '9', '+', '/' }; private static final char intToAltBase64[] = { '!', '"', '#', '$', '%', '&', '\'', '(', ')', ',', '-', '.', ':', ';', '<', '>', '@', '[', ']', '^', '`', '_', '{', '|', '}', '~', 'a', 'b', 'c', 'd', 'e', 'f', 'g', 'h', 'i', 'j', 'k', 'l', 'm', 'n', 'o', 'p', 'q', 'r', 's', 't', 'u', 'v', 'w', 'x', 'y', 'z', '0', '1', '2', '3', '4', '5', '6', '7', '8', '9', '+', '?' }; private static final byte base64ToInt[] = { -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, 62, -1, -1, -1, 63, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, -1, -1, -1, -1, -1, -1, -1, 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, -1, -1, -1, -1, -1, -1, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51 }; private static final byte altBase64ToInt[] = { -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, 0, 1, 2, 3, 4, 5, 6, 7, 8, -1, 62, 9, 10, 11, -1, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 12, 13, 14, -1, 15, 63, 16, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, 17, -1, 18, 19, 21, 20, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 22, 23, 24, 25 }; }