Java code To convert byte to Hexadecimal

Question

I have an array of bytes  I want each byte String of that array to be converted to its corresponding hexadecimal values   Is there any function in Java to convert a byte array to Hexadecimal

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Java 17  Introducing java util HexFormat Java 17 comes with a utility to convert byte arrays and numbers to their hexadecimal counterparts  Let s say we have an MD5 digest of  quot Hello World quot  as a byte-array  var md5   MessageDigest getInstance  quot md5 quot    md5 update  quot Hello world quot  getBytes UTF 8     var digest   md5 digest     Now we can use the HexFormat of   formatHex byte    method to convert the given byte   to its hexadecimal form  jshell gt  HexFormat of   formatHex digest   7    gt   quot 3e25960a79dbc69b674cd4ec67a72c62 quot   The withUpperCase   method returns the uppercase version of the previous output  jshell gt  HexFormat of   withUpperCase   formatHex digest   8    gt   quot 3E25960A79DBC69B674CD4EC67A72C62 quot

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Creating  and destroying  a bunch of String instances is not a good way if performance is an issue   Please ignore those verbose  duplicate  arguments checking statements  ifs   That s for  another  educational purposes    Full maven project  http   jinahya googlecode com svn trunk com googlecode jinahya hex-codec   Encoding            Encodes a single nibble         param decoded the nibble to encode         return the encoded half octet      protected static int encodeHalf final int decoded         switch  decoded            case 0x00          case 0x01          case 0x02          case 0x03          case 0x04          case 0x05          case 0x06          case 0x07          case 0x08          case 0x09              return decoded   0x30     0x30  0   - 0x39  9           case 0x0A          case 0x0B          case 0x0C          case 0x0D          case 0x0E          case 0x0F              return decoded   0x57     0x41  a   - 0x46  f           default              throw new IllegalArgumentException  illegal half      decoded                    Encodes a single octet into two nibbles         param decoded the octet to encode      param encoded the array to which each encoded nibbles are written      param offset the offset in the array      protected static void encodeSingle final int decoded  final byte   encoded                                     final int offset         if  encoded    null            throw new IllegalArgumentException  null encoded               if  encoded length  lt  2               not required         throw new IllegalArgumentException               encoded length     encoded length       lt  2               if  offset  lt  0            throw new IllegalArgumentException  offset     offset       lt  0               if  offset  gt   encoded length - 1            throw new IllegalArgumentException               offset     offset       gt   encoded length     encoded length                  - 1               encoded offset     byte  encodeHalf  decoded  gt  gt  4   amp  0x0F       encoded offset   1     byte  encodeHalf decoded  amp  0x0F              Decodes given sequence of octets into a sequence of nibbles         param decoded the octets to encode        return the encoded nibbles      protected static byte   encodeMultiple final byte   decoded         if  decoded    null            throw new IllegalArgumentException  null decoded               final byte   encoded   new byte decoded length  lt  lt  1        int offset   0      for  int i   0  i  lt  decoded length  i              encodeSingle decoded i   encoded  offset           offset    2             return encoded             Encodes given sequence of octets into a sequence of nibbles         param decoded the octets to encode         return the encoded nibbles      public byte   encode final byte   decoded         return encodeMultiple decoded       Decoding            Decodes a single nibble         param encoded the nibble to decode         return the decoded half octet      protected static int decodeHalf final int encoded         switch  encoded            case 0x30      0          case 0x31      1          case 0x32      2          case 0x33      3          case 0x34      4          case 0x35      5          case 0x36      6          case 0x37      7          case 0x38      8          case 0x39      9              return encoded - 0x30          case 0x41      A          case 0x42      B          case 0x43      C          case 0x44      D          case 0x45      E          case 0x46      F              return encoded - 0x37          case 0x61      a          case 0x62      b          case 0x63      c          case 0x64      d          case 0x65      e          case 0x66      f              return encoded - 0x57          default              throw new IllegalArgumentException  illegal half      encoded                    Decodes two nibbles into a single octet         param encoded the nibble array      param offset the offset in the array         return decoded octet      protected static int decodeSingle final byte   encoded  final int offset         if  encoded    null            throw new IllegalArgumentException  null encoded               if  encoded length  lt  2               not required         throw new IllegalArgumentException               encoded length     encoded length       lt  2               if  offset  lt  0            throw new IllegalArgumentException  offset     offset       lt  0               if  offset  gt   encoded length - 1            throw new IllegalArgumentException               offset     offset       gt   encoded length     encoded length                  - 1               return  decodeHalf encoded offset    lt  lt  4               decodeHalf encoded offset   1               Encodes given sequence of nibbles into a sequence of octets         param encoded the nibbles to decode         return the encoded octets      protected static byte   decodeMultiple final byte   encoded         if  encoded    null            throw new IllegalArgumentException  null encoded               if   encoded length  amp  0x01     0x01            throw new IllegalArgumentException               encoded length     encoded length      is not even               final byte   decoded   new byte encoded length  gt  gt  1        int offset   0      for  int i   0  i  lt  decoded length  i              decoded i     byte  decodeSingle encoded  offset           offset    2             return decoded             Decodes given sequence of nibbles into a sequence of octets         param encoded the nibbles to decode         return the decoded octets      public byte   decode final byte   encoded         return decodeMultiple encoded

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byte   bytes    -1  0  1  2  3        StringBuilder sb   new StringBuilder        for  byte b   bytes            sb append String format   02X    b              System out println sb toString            prints  FF 00 01 02 03     See also   java util Formatter syntax     flags  width conversion   Flag  0  - The result will be zero-padded  Width 2 Conversion  X  - The result is formatted as a hexadecimal integer  uppercase       Looking at the text of the question  it s also possible that this is what is requested       String   arr     -1    0    10    20         for  int i   0  i  lt  arr length  i              arr i    String format   02x   Byte parseByte arr i               System out println java util Arrays toString arr           prints   ff  00  0a  14       Several answers here uses Integer toHexString int   this is doable  but with some caveats  Since the parameter is an int  a widening primitive conversion is performed to the byte argument  which involves sign extension       byte b   -1      System out println Integer toHexString b           prints  ffffffff    The 8-bit byte  which is signed in Java  is sign-extended to a 32-bit int  To effectively undo this sign extension  one can mask the byte with 0xFF       byte b   -1      System out println Integer toHexString b  amp  0xFF           prints  ff    Another issue with using toHexString is that it doesn t pad with zeroes       byte b   10      System out println Integer toHexString b  amp  0xFF           prints  a    Both factors combined should make the String format solution more preferrable   References   JLS 4 2 1 Integral Types and Values   For byte  from -128 to 127  inclusive  JLS 5 1 2 Widening Primitive Conversion

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Others have covered the general case  But if you have a byte array of a known form  for example a MAC address  then you can   byte   mac      byte 0x00   byte 0x00   byte 0x00   byte 0x00   byte 0x00     String str   String format   02X  02X  02X  02X  02X  02X                              mac 0   mac 1   mac 2   mac 3   mac 4   mac 5

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This is the code that I ve found to run the fastest so far  I ran it on 109015 byte arrays of length 32  in 23ms  I was running it on a VM so it ll probably run faster on bare metal   public static final char   HEX DIGITS             0    1    2    3    4    5    6    7    8    9    A    B    C    D    E    F     public static char   encodeHex  final byte   data        final int l   data length      final char   out   new char l lt  lt 1       for  int i 0 j 0  i lt l  i              out j      HEX DIGITS  0xF0  amp  data i    gt  gt  gt  4           out j      HEX DIGITS 0x0F  amp  data i              return out      Then you can just do   String s   new String  encodeHex myByteArray

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If you use Tink  then there is  package com google crypto tink subtle   public final class Hex     public static String encode final byte   bytes            public static byte   decode String hex             so something like this should work  import com google crypto tink subtle Hex   byte   bytes    -1  0  1  2  3    String enc   Hex encode bytes   byte   dec   Hex decode enc

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I am posting because none of the existing answers explain why their approaches work  which I think is really important for this problem  In some cases  this causes the proposed solution to appear unnecessarily complicated and subtle   To illustrate I will provide a fairly straightforward approach  but I ll provide a bit more detail to help illustrate why it works   First off  what are we trying to do  We want to convert a byte value  or an array of bytes  to a string which represents a hexadecimal value in ASCII  So step one is to find out exactly what a byte in Java is      The byte data type is an 8-bit signed two s complement integer  It has a minimum value of -128 and a maximum value of 127  inclusive   The byte data type can be useful for saving memory in large arrays  where the memory savings actually matters  They can also be used in place of int where their limits help to clarify your code  the fact that a variable s range is limited can serve as a form of documentation    What does this mean  A few things  First and most importantly  it means we are working with 8-bits  So for example we can write the number 2 as 0000 0010  However  since it is two s complement  we write a negative 2 like this  1111 1110  What is also means is that converting to hex is very straightforward  That is  you simply convert each 4 bit segment directly to hex  Note that to make sense of negative numbers in this scheme you will first need to understand two s complement  If you don t already understand two s complement  you can read an excellent explanation  here  http   www cs cornell edu  tomf notes cps104 twoscomp html    Converting Two s Complement to Hex In General  Once a number is in two s complement it is dead simple to convert it to hex  In general  converting from binary to hex is very straightforward  and as you will see in the next two examples  you can go directly from two s complement to hex    Examples  Example 1  Convert 2 to Hex    1  First convert 2 to binary in two s complement    2  base 10    0000 0010  base 2    2  Now convert binary to hex   0000   0x0 in hex 0010   0x2 in hex  therefore 2   0000 0010   0x02     Example 2  Convert -2  in two s complement  to Hex   1  First convert -2 to binary in two s complement    -2  base 10    0000 0010  direct conversion to binary                  1111 1101  invert bits                 1111 1110  add 1  therefore  -2   1111 1110  in two s complement    2  Now Convert to Hex   1111   0xF in hex 1110   0xE in hex  therefore  -2   1111 1110   0xFE      Doing this In Java  Now that we ve covered the concept  you ll find we can achieve what we want with some simple masking and shifting  The key thing to understand is that the byte you are trying to convert is already in two s complement  You don t do this conversion yourself  I think this is a major point of confusion on this issue  Take for example the follow byte array   byte   bytes   new byte   -2 2     We just manually converted them to hex  above  but how can we do it in Java  Here s how    Step 1  Create a StringBuffer to hold our computation     StringBuffer buffer   new StringBuffer      Step 2  Isolate the higher order bits  convert them to hex  and append them to the buffer  Given the binary number 1111 1110  we can isolate the higher order bits by first shifting them over by 4  and then zeroing out the rest of the number  Logically this is simple  however  the implementation details in Java  and many languages  introduce a wrinkle because of sign extension  Essentially  when you shift a byte value  Java first converts your value to an integer  and then performs sign extension  So while you would expect 1111 1110    4 to be 0000 1111  in reality  in Java it is represented as the two s complement 0xFFFFFFFF   So returning to our example    1111 1110  gt  gt  4  shift right 4    1111 1111 1111 1111 1111 1111 1111 1111  32 bit sign-extended number in two s complement    We can then isolate the bits with a mask   1111 1111 1111 1111 1111 1111 1111 1111  amp  0xF   0000 0000 0000 0000 0000 0000 0000 1111 therefore  1111   0xF in hex     In Java we can do this all in one shot   Character forDigit  bytes 0   gt  gt  4   amp  0xF  16     The forDigit function just maps the number you pass it onto the set of hexadecimal numbers 0-F    Step 3  Next we need to isolate the lower order bits  Since the bits we want are already in the correct position  we can just mask them out   1111 1110  amp  0xF   0000 0000 0000 0000 0000 0000 0000 1110  recall sign extension from before  therefore  1110   0xE in hex      Like before  in Java we can do this all in one shot   Character forDigit  bytes 0   amp  0xF   16     Putting this all together we can do it as a for loop and convert the entire array   for int i 0  i  lt  bytes length  i         buffer append Character forDigit  bytes i   gt  gt  4   amp  0xF  16        buffer append Character forDigit  bytes i   amp  0xF   16        Hopefully this explanation makes things clearer for those of you wondering exactly what is going on in the many examples you will find on the internet  Hopefully I didn t make any egregious errors  but suggestions and corrections are highly welcome

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Here is a simple function to convert byte to Hexadecimal     private static String convertToHex byte   data        StringBuffer buf   new StringBuffer        for  int i   0  i  lt  data length  i              int halfbyte    data i   gt  gt  gt  4   amp  0x0F          int two halfs   0          do               if   0  lt   halfbyte   amp  amp   halfbyte  lt   9                   buf append  char    0    halfbyte                else                 buf append  char    a     halfbyte - 10                 halfbyte   data i   amp  0x0F            while two halfs    lt  1             return buf toString

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A short and simple way to convert byte   to hex string by using BigInteger   import java math BigInteger   byte   bytes   new byte     byte 255  10  20  30   String hex   new BigInteger 1  bytes  toString 16   System out println hex      ff0a141e   How It Works   The built-in system class java math BigInteger class  java math BigInteger  is compatible with binary and hex data    Its has a constructor BigInteger signum 1  byte    to create a big integer by byte    set its first parameter signum   1 to handle correctly the negative bytes  Use BigInteger toString 16  to convert the big integer to hex string To parse a hex number use new BigInteger  ffa74b   16  - does not handle correctly the leading zero   If you may want to have the leading zero in the hex result  check its size and add the missing zero if necessary   if  hex length     2    1      hex    0    hex    Notes  Use new BigInteger 1  bytes   instead of new BigInteger bytes   because Java is  broken by design  and the byte data type does not hold bytes but signed tiny integers  -128   127   If the first byte is negative  the BigInteger assumes you pass a negative big integer  Just pass 1 as first parameter  signum 1    The conversion back from hex to byte   is tricky  sometimes a leading zero enters in the produced output and it should be cleaned like this   byte   bytes   new BigInteger  ffa74b   16  toByteArray    if  bytes 0     0        byte   newBytes   new byte bytes length - 1       System arraycopy bytes  1  newBytes  0  newBytes length       bytes   newBytes      The last note is the if the byte   has several leading zeroes  they will be lost

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If you are happy to use an external library  the org apache commons codec binary Hex class has an encodeHex method which takes a byte   and returns a char    This methods is MUCH faster than the format option  and encapsulates the details of the conversion  Also comes with a decodeHex method for the opposite conversion

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You can use the method from Bouncy Castle Provider library   org bouncycastle util encoders Hex toHexString byteArray        The Bouncy Castle Crypto package is a Java implementation of   cryptographic algorithms  This jar contains JCE provider and   lightweight API for the Bouncy Castle Cryptography APIs for JDK 1 5 to   JDK 1 8    Maven dependency    lt dependency gt       lt groupId gt org bouncycastle lt  groupId gt       lt artifactId gt bcprov-jdk15on lt  artifactId gt       lt version gt 1 60 lt  version gt   lt  dependency gt    or from Apache Commons Codec   org apache commons codec binary Hex encodeHexString byteArray        The Apache Commons Codec package contains simple encoder and decoders   for various formats such as Base64 and Hexadecimal  In addition to   these widely used encoders and decoders  the codec package also   maintains a collection of phonetic encoding utilities    Maven dependency    lt dependency gt       lt groupId gt commons-codec lt  groupId gt       lt artifactId gt commons-codec lt  artifactId gt       lt version gt 1 11 lt  version gt   lt  dependency gt

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There s your fast method       private static final String   hexes   new String             00   01   02   03   04   05   06   07   08   09   0A   0B   0C   0D   0E   0F            10   11   12   13   14   15   16   17   18   19   1A   1B   1C   1D   1E   1F            20   21   22   23   24   25   26   27   28   29   2A   2B   2C   2D   2E   2F            30   31   32   33   34   35   36   37   38   39   3A   3B   3C   3D   3E   3F            40   41   42   43   44   45   46   47   48   49   4A   4B   4C   4D   4E   4F            50   51   52   53   54   55   56   57   58   59   5A   5B   5C   5D   5E   5F            60   61   62   63   64   65   66   67   68   69   6A   6B   6C   6D   6E   6F            70   71   72   73   74   75   76   77   78   79   7A   7B   7C   7D   7E   7F            80   81   82   83   84   85   86   87   88   89   8A   8B   8C   8D   8E   8F            90   91   92   93   94   95   96   97   98   99   9A   9B   9C   9D   9E   9F            A0   A1   A2   A3   A4   A5   A6   A7   A8   A9   AA   AB   AC   AD   AE   AF            B0   B1   B2   B3   B4   B5   B6   B7   B8   B9   BA   BB   BC   BD   BE   BF            C0   C1   C2   C3   C4   C5   C6   C7   C8   C9   CA   CB   CC   CD   CE   CF            D0   D1   D2   D3   D4   D5   D6   D7   D8   D9   DA   DB   DC   DD   DE   DF            E0   E1   E2   E3   E4   E5   E6   E7   E8   E9   EA   EB   EC   ED   EE   EF            F0   F1   F2   F3   F4   F5   F6   F7   F8   F9   FA   FB   FC   FD   FE   FF              public static String byteToHex byte b            return hexes b amp 0xFF

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If you like streams  here is a single-expression version of the format-and-concatenate approach  String hex   IntStream range 0  bytes length                         map i - gt  bytes i   amp  0xff                         mapToObj b - gt  String format  quot  02x quot   b                          collect Collectors joining      It s a shame there isn t a method like Arrays  streamUnsignedBytes for this

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This is a very fast way  No external libaries needed   final protected static char   HEXARRAY    0123456789abcdef  toCharArray         public static String encodeHexString  byte   bytes              char   hexChars   new char bytes length   2           for  int j   0  j  lt  bytes length  j                  int v   bytes j   amp  0xFF              hexChars j   2    HEXARRAY v  gt  gt  gt  4               hexChars j   2   1    HEXARRAY v  amp  0x0F                     return new String hexChars

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The fastest way i ve yet found to do this is the following   private static final String    HEXES       0123456789ABCDEF    static String getHex byte   raw        final StringBuilder hex   new StringBuilder 2   raw length       for  final byte b   raw            hex append HEXES charAt  b  amp  0xF0   gt  gt  4   append HEXES charAt  b  amp  0x0F               return hex toString        It s   50x faster than String format  if you want to test it   public class MyTest      private static final String    HEXES           0123456789ABCDEF         Test     public void test get hex             byte   raw                  byte  0xd0   byte  0x0b   byte  0x01   byte  0x2a   byte  0x63               byte  0x78   byte  0x01   byte  0x2e   byte  0xe3   byte  0x6c               byte  0xd2   byte  0xb0   byte  0x78   byte  0x51   byte  0x73               byte  0x34   byte  0xaf   byte  0xbb   byte  0xa0   byte  0x9f               byte  0xc3   byte  0xa9   byte  0x00   byte  0x1e   byte  0xd5               byte  0x4b   byte  0x89   byte  0xa3   byte  0x45   byte  0x35               byte  0xd6   byte  0x10                      int N   77777          long t                         t   System currentTimeMillis                for  int i   0  i  lt  N  i                      final StringBuilder hex   new StringBuilder 2   raw length                   for  final byte b   raw                        hex append HEXES charAt  b  amp  0xF0   gt  gt  4   append HEXES charAt  b  amp  0x0F                                       hex toString                              System out println System currentTimeMillis   - t      50                                  t   System currentTimeMillis                for  int i   0  i  lt  N  i                      StringBuilder hex   new StringBuilder 2   raw length                   for  byte b   raw                        hex append String format   02X   b                                      hex toString                              System out println System currentTimeMillis   - t      2535                      Edit  Just found something just a lil faster and that holds on one line but is not compatible with JRE 9  Use at your own risks  import javax xml bind DatatypeConverter   DatatypeConverter printHexBinary raw

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Try this way   byte bv   10  String hexString   Integer toHexString bv     Dealing with array  if I understood you correctly    byte   bytes    9  10  11  15  16   StringBuffer result   new StringBuffer    for  byte b   bytes        result append String format   02X    b        result append          delimiter   return result toString      As polygenelubricants mentioned  String format   is the right answer compare to Integer toHexString    since it deals with negative numbers in a right way

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The Best solution is this badass one-liner   String hex DatatypeConverter printHexBinary byte   b     as mentioned here

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I couldn t figure out what exactly you meant by byte String  but here are some conversions from byte to String and vice versa  of course there is a lot more on the official documentations  Integer intValue   149    The corresponding byte value is   Byte byteValue   intValue byteValue       this will convert the rightmost byte of the intValue to byte  because Byte is an 8 bit object and Integer is at least 16 bit  and it will give you a signed number in this case -107   get the integer value back from a Byte variable   Integer anInt   byteValue intValue       This will convert the byteValue variable to a signed Integer   From Byte and Integer to hex String  This is the way I do it     Integer anInt   149 Byte aByte   anInt byteValue     String hexFromInt      format  0x x   anInt      This will output 0x95 String hexFromByte      format  0x x   aByte      This will output 0x95   Converting an array of bytes to a hex string  As far as I know there is no simple function to convert all the elements inside an array of some Object to elements of another Object  So you have to do it yourself  You can use the following functions   From byte   to String       public static String byteArrayToHexString byte   byteArray           String hexString                for int i   0  i  lt  byteArray length  i                 String thisByte      format   x   byteArray i                hexString    thisByte                     return hexString          And from hex string to byte     public static byte   hexStringToByteArray String hexString       byte   bytes   new byte hexString length     2        for int i   0  i  lt  hexString length    i    2           String sub   hexString substring i  i   2           Integer intVal   Integer parseInt sub  16           bytes i   2    intVal byteValue            String hex      format  0x x   bytes i   2               return bytes        It is too late but I hope this could help some others

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Use   Integer toHexString  int b

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BigInteger n   new BigInteger byteArray   String hexa   n toString 16

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Just like some other answers  I recommend to use String format   and BigInteger  But to interpret the byte array as big-endian binary representation instead of two s-complement binary representation  with signum and incomplete use of possible hex values range  use BigInteger int signum  byte   magnitude   not BigInteger byte   val    For example  for a byte array of length 8 use   String format   016X   new BigInteger 1 bytes     Advantages    leading zeros no signum only built-in functions only one line of code   Disadvantage    there might be more efficient ways to do that   Example   byte   bytes   new byte 8   Random r   new Random    System out println  big-endian         two s-complement    System out println  ----------------- -----------------    for  int i   0  i  lt  10  i          r nextBytes bytes       System out print String format   016X   new BigInteger 1 bytes         System out print             System out print String format   016X   new BigInteger bytes         System out println        Example output   big-endian         two s-complement ----------------- ----------------- 3971B56BC7C80590   3971B56BC7C80590 64D3C133C86CCBDC   64D3C133C86CCBDC B232EFD5BC40FA61   -4DCD102A43BF059F CD350CC7DF7C9731   -32CAF338208368CF 82CDC9ECC1BC8EED   -7D3236133E437113 F438C8C34911A7F5   -BC7373CB6EE580B 5E99738BE6ACE798   5E99738BE6ACE798 A565FE5CE43AA8DD   -5A9A01A31BC55723 032EBA783D2E9A9F   032EBA783D2E9A9F 8FDAA07263217ABA   -70255F8D9CDE8546

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If you want a constant-width hex representation  i e  0A instead of A  so that you can recover the bytes unambiguously  try format     StringBuilder result   new StringBuilder    for  byte bb   byteArray        result append String format   02X   bb      return result toString

[java] Java code To convert byte to Hexadecimal

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