How to convert byte array to string and vice versa

Question

I have to convert a byte array to string in Android  but my byte array contains negative values   If I convert that string again to byte array  values I am getting are different from original byte array values   What can I do to get proper conversion  Code I am using to do the conversion is as follows      Code to convert byte arr to str  byte   by original    0 1 -2 3 -4 -5 6   String str1   new String by original   System out println  str1  gt  gt    str1       Code to convert str to byte arr  byte   by new   str1 getBytes    for int i 0 i lt by new length i     System out println  by1   i     gt  gt    str1     I am stuck in this problem

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Even though   new String bytes   UTF-8     is correct it throws a UnsupportedEncodingException which forces you to deal with a checked exception  You can use as an alternative another constructor since Java 1 6 to convert a byte array into a String   new String bytes  StandardCharsets UTF 8    This one does not throw any exception   Converting back should be also done with StandardCharsets UTF 8    test  getBytes StandardCharsets UTF 8    Again you avoid having to deal with checked exceptions

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InputStream is   new FileInputStream   home kalt Desktop SUDIS READY ds bin    byte   bytes   IOUtils toByteArray is

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Heres a few methods that convert an array of bytes to a string  I ve tested them they work well   public String getStringFromByteArray byte   settingsData         ByteArrayInputStream byteArrayInputStream   new ByteArrayInputStream settingsData       Reader reader   new BufferedReader new InputStreamReader byteArrayInputStream        StringBuilder sb   new StringBuilder        int byteChar       try           while  byteChar   reader read       -1                sb append  char  byteChar                       catch IOException e            e printStackTrace               return sb toString        public String getStringFromByteArray byte   settingsData         StringBuilder sb   new StringBuilder        for byte willBeChar  settingsData            sb append  char  willBeChar              return sb toString

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While base64 encoding is safe and one could argue  the right answer   I arrived here looking for a way to convert a Java byte array to from a Java String as-is  That is  where each member of the byte array remains intact in its String counterpart  with no extra space required for encoding transport   This answer describing 8bit transparent encodings was very helpful for me  I used ISO-8859-1 on terabytes of binary data to convert back and forth successfully  binary  lt -  String  without the inflated space requirements needed for a base64 encoding  so is safe for my use-case - YMMV   This was also helpful in explaining when if you should experiment

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The root problem is  I think  that you are unwittingly using a character set for which    bytes    encode decode bytes     in some cases   UTF-8 is an example of such a character set   Specifically  certain sequences of bytes are not valid encodings in UTF-8   If the UTF-8 decoder encounters one of these sequences  it is liable to discard the offending bytes or decode them as the Unicode codepoint for  no such character    Naturally  when you then try to encode the characters as bytes the result will be different   The solution is    Be explicit about the character encoding you are using  i e  use a String constructor and String toByteArray method with an explicit charset  Use the right character set for your byte data     or alternatively one  such as  Latin-1  where all byte sequences map to valid Unicode characters  If your bytes are  really  binary data and you want to be able to transmit   receive them over a  text based  channel  use something like Base64 encoding     which is designed for this purpose

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Using new String byOriginal  and converting back to byte   using getBytes   doesn t guarantee two byte   with equal values  This is due to a call to StringCoding encode     which will encode the String to Charset defaultCharset    During this encoding  the encoder might choose to replace unknown characters and do other changes  Hence  using String getBytes   might not return an equal array as you ve originally passed to the constructor

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The  proper conversion  between byte   and String is to explicitly state the encoding you want to use  If you start with a byte   and it does not in fact contain text data  there is no  proper conversion   Strings are for text  byte   is for binary data  and the only really sensible thing to do is to avoid converting between them unless you absolutely have to   If you really must use a String to hold binary data then the safest way is to use Base64 encoding

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javax xml bind DatatypeConverter should do it   byte    b   javax xml bind DatatypeConverter parseHexBinary  E62DB    String s   javax xml bind DatatypeConverter printHexBinary b

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import sun misc BASE64Decoder  import sun misc BASE64Encoder       private static String base64Encode byte   bytes        return new BASE64Encoder   encode bytes      private static byte   base64Decode String s  throws IOException       return new BASE64Decoder   decodeBuffer s

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We just need to construct a new String with the array  http   www mkyong com java how-do-convert-byte-array-to-string-in-java   String s   new String bytes     The bytes of the resulting string differs depending on what charset you use  new String bytes  and new String bytes  Charset forName  utf-8    and new String bytes  Charset forName  utf-16    will all have different byte arrays when you call String getBytes    depending on the default charset

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This works fine for me   String cd  Holding some value     Converting from string to byte     byte   cookie   new sun misc BASE64Decoder   decodeBuffer cd     Converting from byte   to string   cd   new sun misc BASE64Encoder   encode cookie

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I succeeded converting byte array to a string with this method   public static String byteArrayToString byte   data       String response   Arrays toString data        String   byteValues   response substring 1  response length   - 1  split           byte   bytes   new byte byteValues length        for  int i 0  len bytes length  i lt len  i              bytes i    Byte parseByte byteValues i  trim                String str   new String bytes       return str toLowerCase

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public class byteString                    param args             public static void main String   args  throws Exception              TODO Auto-generated method stub         String msg    Hello           byte   buff   new byte 1024           buff   msg getBytes  UTF-8            System out println buff           String m   new String buff           System out println m

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A string is a collection of char s  16bit unsigned   So if you are going to convert negative numbers into a string  they ll be lost in translation

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Here the working code                  Encode byte array into string   TemplateBuffer1 is my bytearry variable           String finger buffer   Base64 encodeToString templateBuffer1  Base64 DEFAULT           Log d TAG   Captured biometric device- gt     finger buffer                Decode String into Byte Array  decodedString is my bytearray            decodedString   Base64 decode finger buffer  Base64 DEFAULT

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Read the bytes from String using ByteArrayInputStream and wrap it with BufferedReader which is Char Stream instead of Byte Stream which converts the byte data to String   package com cs sajal   import java io BufferedReader  import java io ByteArrayInputStream  import java io InputStreamReader  import java io UnsupportedEncodingException   public class TestCls        public static void main String   args             String s new String  Sajal is  a good boy             try                   ByteArrayInputStream bis          bis new ByteArrayInputStream s getBytes  UTF-8              BufferedReader br new BufferedReader new InputStreamReader bis            System out println br readLine                        catch Exception e                        e printStackTrace                         Output is      Sajal is  a good boy

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This one works for me up to android Q  You can use the following method to convert o hex string to string     public static String hexToString String hex        StringBuilder sb   new StringBuilder        char   hexData   hex toCharArray        for  int count   0  count  lt  hexData length - 1  count    2            int firstDigit   Character digit hexData count   16           int lastDigit   Character digit hexData count   1   16           int decimal   firstDigit   16   lastDigit          sb append  char decimal             return sb toString       with the following to convert a byte array to a hex string     public static String bytesToHex 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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Try to specify an 8-bit charset in both conversions  ISO-8859-1 for instance

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You can use simple for loop for conversion   public void byteArrToString       byte   b     a   b           String str           for int i 0  i lt b length  i            char c    char  b i          str  c          System out println str

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Why was the problem  As someone already specified   If you start with a byte   and it does not in fact contain text data  there is no  proper conversion   Strings are for text  byte   is for binary data  and the only really sensible thing to do is to avoid converting between them unless you absolutely have to   I was observing this problem when I was trying to create byte   from a pdf file and then converting it to String and then taking the String as input and converting back to file    So make sure your encoding and decoding logic is same as I did  I explicitly encoded the byte   to Base64 and decoded it to create the file again   Use-case  Due to some limitation I was trying to sent byte   in request POST  and the process was as follows   PDF File    Base64 encodeBase64 byte       String    Send in request POST     receive String    Base64 decodeBase64 byte       create binary  Try this and this worked for me    File file   new File  filePath             byte   byteArray   new byte  int  file length              try               FileInputStream fileInputStream   new FileInputStream file               fileInputStream read byteArray                String byteArrayStr  new String Base64 encodeBase64 byteArray                 FileOutputStream fos   new FileOutputStream  newFilePath                fos write Base64 decodeBase64 byteArrayStr getBytes                  fos close                       catch  FileNotFoundException e                System out println  File Not Found                 e printStackTrace                      catch  IOException e1                System out println  Error Reading The File                 e1 printStackTrace

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I did notice something that is not in any of the answers  You can cast each of the bytes in the byte array to characters  and put them in a char array  Then the string is new String cbuf  where cbuf is the char array  To convert back  loop through the string casting each of the chars to bytes to put into a byte array  and this byte array will be the same as the first    public class StringByteArrTest        public static void main String   args               put whatever byte array here         byte   arr   new byte    -12  -100  -49  100  -63  0  -90           for  byte b  arr  System out println b              put data into this char array         char   cbuf   new char arr length           for  int i   0  i  lt  arr length  i                  cbuf i     char  arr i                        this is the string         String s   new String cbuf           System out println s               converting back         byte   out   new byte s length             for  int i   0  i  lt  s length    i                  out i     byte  s charAt i                     for  byte b  out  System out println b

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private static String toHexadecimal byte   digest           String hash           for byte aux   digest            int b   aux  amp  0xff          if  Integer toHexString b  length      1  hash     0           hash    Integer toHexString b             return hash

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Your byte array must have some encoding  The encoding cannot be ASCII if you ve got negative values  Once you figure that out  you can convert a set of bytes to a String using  byte   bytes         String str   new String bytes  StandardCharsets UTF 8      for UTF-8 encoding  There are a bunch of encodings you can use  look at the supported encodings in the Oracle javadocs

[java] How to convert byte array to string and vice versa?

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