Java converts bytes to hexadecimal code sharing

/** * reference apache commons <a * href="http://commons.apache.org/codec/">http://commons.apache.org/codec/</a> * * byte takes 8 bits and hexadecimal characters take 4 bits. Therefore, a byte can be converted into two corresponding hexadecimal characters, that is, the high 4 bits of byte and the low 4 bits * are converted into the corresponding hexadecimal characters H and L, and combined. The same goes for the opposite conversion. ** / public class Hex {/** ** Used to create the output of hexadecimal characters */ private static final char[] DIGITS_LOWER = {'0', '1', '2', '3', '4', '5', '6', '7', '8', '9', 'a', 'b', 'c', 'd', 'e', 'f' }; / * * * is used to establish the output of the hexadecimal character * / private static final char [] DIGITS_UPPER = {' 0 ', '1', '2', '3', '4', '5', '6', '7', '8', '9', 'A', 'B', 'C', 'D', 'E', 'F' }; /** * Converts a byte array to a hexadecimal character array. * * Because two characters are used to represent a byte, the length of the returned char[] will be twice the length of the parameter byte[]. * * @param data * byte[] * @return char containing hexadecimal characters [] */ public static char[] encodeHex(final byte[] data) { return encodeHex(data, true); } /** * Converts a byte array to a hexadecimal character array. * * Because two characters are used to represent a byte, the length of the returned char[] will be twice the length of the parameter byte[]. * * @param data * byte[] * @param toLowerCase * <code>true</code> Convert to lowercase, <code>false</code> Convert to uppercase format * @return contains hexadecimal characters char[] */ public static char[] encodeHex(final byte[] data, final boolean toLowerCase) { return encodeHex(data, toLowerCase ? DIGITS_LOWER : DIGITS_UPPER); } /** * Converts a byte array to a hexadecimal character array. * * Because two characters are used to represent a byte, the length of the returned char[] will be twice the length of the parameter byte[]. * * @param data * byte[] * @param toDigits * Alphabet for controlling output * @return char containing hexadecimal characters [] */ protected static char[]  encodeHex(final byte[] data, final char[] toDigits) { int l = data.length; char[] out = new char[l << 1]; // two characters form the hex value. for (int i = 0, j = 0; i < l; i++) { out[j++] = toDigits[(0xF0 & data[i]) >>> 4]; out[j++] = toDigits[0x0F & data[i]]; } return out; } /** * Converts a byte array to a hexadecimal string. * * Because two characters are used to represent a byte, the returned string length will be twice the length of the parameter byte[]. * * @param data * byte[] * @return hexadecimal String */ public static String encodeHexStr(final byte[] data) {return encodeHexStr(data, true); } /** * Converts a byte array to a hexadecimal string. * * Because two characters are used to represent a byte, the returned string length will be twice the length of the parameter byte[]. * * @param data * byte[] * @param toLowerCase * <code>true</code> Convert to lowercase, <code>false</code> Convert to uppercase format * @return hexadecimal String */ public static String encodeHexStr(byte[] data, boolean toLowerCase) { return encodeHexStr(data, toLowerCase ? DIGITS_LOWER : DIGITS_UPPER); } /** * Converts a byte array to a hexadecimal string. * * Because two characters are used to represent a byte, the returned string length will be twice the length of the parameter byte[]. * * @param data * byte[] * @param toDigits * Alphabet used to control output * @return hexadecimal String */ protected static String encodeHexStr(byte[] data, char[] toDigits) { return new String(encodeHex(data, toDigits)); } /** * Converts hexadecimal character array to byte array ** @param data * hexadecimal char[] * @return byte[] * @throws RuntimeException * If the length of the source hexadecimal character array is odd, Will throw a runtime exception */ public static byte[] decodeHex(char[] data) {int len = data.length; if ((len & 0x01) ! = 0) { throw new RuntimeException("Odd number of characters."); } // If a byte corresponds to two hexadecimal characters, set the size of byte[] to half the size of char[]. byte[] out = new byte[len >> 1]; // two characters form the hex value. for (int i = 0, j = 0; j < len; i++) { int f = toDigit(data[j], j) << 4; j++; f = f | toDigit(data[j], j); j++; out[i] = (byte) (f & 0xFF); } return out; } /** * Converts the hexadecimal character to an integer. * * @param ch * Character to be converted to an integer * @param index * character position in the character array * @return an integer * @throws RuntimeException * When ch is not a valid hexadecimal character, Throw this exception */ protected static int toDigit(final char ch, final int index) {final int digit = Character.digit(ch, 16); if (digit == -1) { throw new RuntimeException("Illegal hexadecimal character " + ch + " at index " + index); } return digit; } public static void main(String[] args) { String srcStr = "HelloWorld!" ; String encodeStr = encodeHexStr(srcStr.getBytes(), false); String decodeStr = new String(decodeHex(encodeStr.toCharArray())); System.out.println(" Source string: "+ srcStr); System.out.println(" String encoded in hexadecimal: "+ encodeStr); System.out.println(" hexadecimal decoded to string: "+ decodeStr); }}