Java hexadecimal string-hexstring

Java hexadecimal string-hexstring

http://my.oschina.net/xinxingegeya/blog/287476

Byte[] and hexadecimal strings are converted to each other

In Java, Byte uses a binary representation of 8 bits, and we know that each character in the 16 binary needs to be represented by a 4-bit bits.

So we can convert each byte to two corresponding 16 characters, that is, the high 4 and low 4 bits of byte are converted to the corresponding 16-character H and L, and combined to get the result of byte conversion to the 16 binary string.

New String (H) + new String (L).

In the same way, the opposite conversion also converts two 16 characters into a byte, as in the same principle.

Based on the above, we can convert the byte[] array to a 16 binary string, and of course we can convert the 16 binary string to the byte[] array.

Java code:

package test; public class hex {     /**      *  an array of lowercase characters used to build the output of the hexadecimal character      */    private  static final char[] digits_lower = {' 0 ',  ' 1 ',  ' 2 ',  ' 3 ',  ' 4 ',   ' 5 ',             ' 6 ',  ' 7 ',  ' 8 ',   ' 9 ',  ' a ',  ' B ',  ' C ',  ' d ',  ' e ',  ' F '};     /**      *  an array of uppercase characters used to create 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      *     *  @param  data  byte[]     *  @return   Hex char[]     */     public static char[] encodehex (Byte[] data)  {         return encodehex (data, true);    }      /**     *  convert a byte array to a hexadecimal character array      *      *  @param  data        byte[]      *  @param  toLowerCase <code>true</code>  Convert to lowercase format  , <code>false</code>  convert to uppercase format      *  @return   Hex char[]     */    public static char[]  Encodehex (byte[] data, boolean&Nbsp;tolowercase)  {        return encodehex (data,  Tolowercase ? digits_lower : digits_upper);    }      /**     *  convert a byte array to a hexadecimal character array      *      *  @param  data     byte[]      *  @param  toDigits  char[]     *  for controlling output @return   hex Char []     */    protected static char[] encodehex ( Byte[] data, 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      *     *  @param  data  byte[]     *  @return   Hex string     */     public static string encodehexstr (Byte[] data)  {         retUrn encodehexstr (data, true);    }     /**      *  convert a byte array to a hexadecimal string      *     * @ param data        byte[]     * @ param tolowercase <code>true</code>  converted to lowercase format  , <code>false</code >  convert to uppercase format      *  @return   Hex string     */     public static string encodehexstr (byte[] data, boolean  toLowerCase)  {        return encodehexstr (data,  Tolowercase ? digits_lower : digits_upper);    }      /**     *  convert a byte array to a hexadecimal string      *      *  @param data     byte[]     *  @param  todigits   char[]     *  @return   hex string     * for controlling output /    protected static string encodehexstr (byte[] data, char[]  todigits)  {        return new string (EncodeHex ( data, todigits));    }     /**      *  converts a hexadecimal character array to a byte array      *     *  @param  data   Hex char[]     *  @return  byte[]     * @ throws runtimeexception  if the source hexadecimal character array is a strange length, the run-time exception will be thrown      */     public static byte[] decodehex (Char[] data)  {          int len = data.length;         if  ((len  &AMP;&NBSP;0X01)  != 0)  {             throw new runtimeexception ("odd number of characters.");         }         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],&NBSP;J)  << 4;             j++;            f = f | todigit (DATA[J],&NBSP;J);             j++;             out[i] =  (Byte)   (F&NBSP;&AMP;&NBSP;0XFF);         }         return out;    }      /**     *  convert hexadecimal characters to an integer       *     *  @param  ch     Hex char      *  @param  index  position of hexadecimal characters in a character array      *  @return   An integer      *  @throws  RuntimeException  throws a run-time exception when CH is not a valid hexadecimal character       */    protected static int todigit (Char ch,  int index)  {&nbsP;       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 =  "Qwer";         string encodestr = encodehexstr (SrcStr.getBytes ());      &nbsP;  string decodestr = new string (Decodehex (Encodestr.tochararray ()));         system.out.println ("Before encode:"  + srcStr);         system.out.println ("After encode:"  + encodeStr);         system.out.println ("Convert:"  + decodestr);     } }

You can also use the common codec to encode hex string, the following code fragment,

@Testpublic  void test ()  {    String hello =  " ASDFASDF you have to ASDFASDFASDFASDFL ";    try {         string hexstring = hex.encodehexstring (Hello.getbytes ("Utf-8"));         string hexstring2 = hex.encodehexstring (Hello.getBytes ("ASCII"));         string hexstring3 = hex.encodehexstring ( Hello.getbytes ("GBK"));         string hexstring4 = new  string (Hex.encodehex (Hello.getbytes ("Utf-8"),  false));         system.out.println (hexstring);         system.out.println ( HEXSTRING2);         system.out.println (HEXSTRING3);         system.out.println (hexstrING4);    } catch  (unsupportedencodingexception e)  {         e.printstacktrace ();     }}

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Java hexadecimal string-hexstring