16进制字符串与字节数组之间的转换

待我称王封你为后i 2022-12-29 04:32 216阅读 0赞

### 文章目录 ###

*   *   *  思路
         *  java代码

### 思路 ###

一个16进制数占4位，一个字节8位，意味着一个字节存储两个16进制数。所以我们要将16进制转成一个字节就需要两个16进制数。

1.  从左往右，两两一组将字符分开。
2.  两个字符一组当成一个字节，分别判断两个字符在a-z、A-Z、0-9哪个区间，然后用字符减去a或者A或者0的字符，得到差，如果是A-Z或者a-z，那么需要加10。
3.  将第一个字符当成16进制的高位，并左移4个位。
4.  将3步骤左移4个位之后的字节|(或)第二个字符的字节数，得到这一组的16进制最终的字节。

![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3UwMTM2MzI3NTU_size_16_color_FFFFFF_t_70]

如果是将字节转成十六进制串，则是上面的逆操作。

### java代码 ###

public class HexCode { 
        private static final char[] UPPER_HEX_CHARS =
                { '0', '1', '2', '3', '4', '5', '6', '7', '8', '9', 'A', 'B', 'C', 'D', 'E', 'F'};
    
        private static final char[] LOWER_HEX_CHARS =
                { '0', '1', '2', '3', '4', '5', '6', '7', '8', '9', 'a', 'b', 'c', 'd', 'e', 'f'};
    
        public static char[] encode2char(byte[] bytes, boolean lowercase) { 
            char[] chars = new char[bytes.length*2];
            for (int i = 0; i < chars.length; i = i + 2) { 
                byte b = bytes[i / 2];
    
                char[] HEX_CHARS = LOWER_HEX_CHARS;
                if (!lowercase) { 
                    HEX_CHARS = UPPER_HEX_CHARS;
                }
    
                chars[i] = HEX_CHARS[(b >> 0x4) & 0xf];
                chars[i + 1] = HEX_CHARS[b & 0xf];
            }
            return chars;
        }
    
        public static String encode(byte[] bytes, boolean lowercase) { 
            char[] endata = encode2char(bytes, lowercase);
            return new String(endata);
        }
    
        public static byte[] decode(String data) throws Exception { 
            int len = (data.length()+1)/2;
            byte[] bytes = new byte[len];
            int index = 0;
            for (int i = 1; i< data.length(); i+=2) { 
                char h = data.charAt(i-1);
                char l = data.charAt(i);
    
                bytes[index] = decodeByte(h,l);
                index++;
            }
    
            return bytes;
        }
    
        public static byte decodeByte(char hight, char low) throws Exception { 
            byte data = 0;
            if (hight>='A' && hight <= 'F') { 
                int value = hight-'A'+10;
                data = (byte)(value<<4);
            } else if (hight>='a' && hight <= 'f') { 
                int value = hight-'a'+10;
                data = (byte)(value<<4);
            } else if (hight>='0' && hight <= '9') { 
                int value = hight-'0';
                data = (byte)(value<<4);
            } else { 
                throw new Exception("decode hexadecimal failed");
            }
    
            if (low>='A' && low <= 'F') { 
                int value = low-'A'+10;
                data |= (byte)value;
            } else if (low>='a' && low <= 'f') { 
                int value = low-'a'+10;
                data |= (byte)value;
            } else if (low>='0' && low <= '9') { 
                int value = low-'0';
                data |= (byte)value;
            } else { 
                throw new Exception("decode hexadecimal failed");
            }
    
            return data;
        }
    
        public static void main(String[] args) throws Exception { 
            String hexStr = "C2B109";
            byte[] bs = decode(hexStr);
            for (byte b : bs) { 
                System.out.printf("%08d%n",Integer.valueOf(Integer.toBinaryString(Byte.toUnsignedInt(b))));
            }
            System.out.println(encode(bs,false));
        }
    }

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