java 字节数组与16进制转换

public class HexCodec {

	static final char[] HEX = new char[]{ '0', '1', '2', '3', '4', '5', '6', '7', '8', '9', 'A', 'B', 'C', 'D', 'E', 'F' };

	public static String hexEncode(byte[] buffer) {
		if (buffer.length == 0) {
			return "";
		}
		int holder = 0;
		char[] chars = new char[buffer.length * 2];
		for (int i = 0; i < buffer.length; i++) {
			holder = (buffer[i] & 0xf0) >> 4;
			chars[i * 2] = HEX[holder];
			holder = buffer[i] & 0x0f;
			chars[(i * 2) + 1] = HEX[holder];
		}
		return new String(chars);
	}

	public static byte[] hexDecode(String hex) {
		//A null string returns an empty array
		if (hex == null || hex.length() == 0) {
			return new byte[0];
		} else if (hex.length() < 3) {
			return new byte[]{ (byte)(Integer.parseInt(hex, 16) & 0xff) };
		}
		//Adjust accordingly for odd-length strings
		int count = hex.length();
		int nibble = 0;
		if (count % 2 != 0) {
			count++;
			nibble = 1;
		}
		byte[] buf = new byte[count / 2];
		char c = 0;
		int holder = 0;
		int pos = 0;
		for (int i = 0; i < buf.length; i++) {
		    for (int z = 0; z < 2 && pos<hex.length(); z++) {
		        c = hex.charAt(pos++);
		        if (c >= 'A' && c <= 'F') {
		            c -= 55;
		        } else if (c >= '0' && c <= '9') {
		            c -= 48;
		        } else if (c >= 'a' && c <= 'f') {
		            c -= 87;
		        }
		        if (nibble == 0) {
		            holder = c << 4;
		        } else {
		            holder |= c;
		            buf[i] = (byte)holder;
		        }
		        nibble = 1 - nibble;
		    }
		}
		return buf;
	}

}