几种字符间的转换

1.将字符串转换成固定长度的字符串

public static String getFixedLenStr(String str, int len, char c, boolean fillleft) {
        if (str == null)
            str = "";
        if (str.getBytes().length > len)
            return str.substring(0, len);
        else {
            int len1 = len - str.getBytes().length;
            if (len1 > 0) {
                byte[] b = new byte[len1];
                for (int i = 0; i < len1; i++)
                    b[i] = (byte) c;
                if (fillleft)
                    str = new String(b) + str;
                else
                    str += new String(b);
            }
            return str;
        }
    }

2.将一个字节转换为16进制字符串

 public static String convertByteToHexStr(byte src) {
        byte[] ret = new byte[2];
        ret[0] = (byte) (src >> 4 & 0x0F);
        ret[0] = (byte) (ret[0] > 9 ? (ret[0] - 10 + ‘a‘) : (ret[0] + ‘0‘));
        ret[1] = (byte) (src & 0x0F);
        ret[1] = (byte) (ret[1] > 9 ? (ret[1] - 10 + ‘a‘) : (ret[1] + ‘0‘));
        return new String(ret);
    }

3.将十六进制字符串转换成一个字节

static public byte convertHexStrToByte(String src) {
        byte b1 = ‘0‘, b2 = ‘0‘;
        byte[] b = src.getBytes();
        src = src.toLowerCase();
        if (b.length > 1) {
            b2 = b[1];
            b1 = b[0];
        } else if (b.length > 0)
            b2 = b[0];
        b1 = (byte) (b1 > ‘9‘ ? b1 - ‘a‘ + 10 : b1 - ‘0‘);
        b2 = (byte) (b2 > ‘9‘ ? b2 - ‘a‘ + 10 : b2 - ‘0‘);
        return (byte) (b1 << 4 | b2);
    }