Converting byte array to String Java

Question

I m writing a web application in Google app Engine  It allows people to basically edit html code that gets stored as an  html file in the blobstore   I m using fetchData to return a byte   of all the characters in the file  I m trying to print to an html  in order for the user to edit the html code  Everything works great   Here s my only problem now   The byte array is having some issues when converting back to a string  Smart quotes and a couple of characters are coming out looking funky     s or japanese symbols etc   Specifically it s several bytes I m seeing that have negative values which are causing the problem   The smart quotes are coming back as -108 and -109 in the byte array  Why is this and how can I decode the negative bytes to show the correct character encoding

User · Answer

Java 7 and above   You can also pass your desired encoding to the String constructor as a Charset constant from StandardCharsets  This may be safer than passing the encoding as a String  as suggested in the other answers   For example  for UTF-8 encoding  String bytesAsString   new String bytes  StandardCharsets UTF 8

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public class Main                   Example method for converting a byte to a String              public void convertByteToString              byte b   65             Using the static toString method of the Byte class         System out println Byte toString b               Using simple concatenation with an empty String         System out println b                   Creating a byte array and passing it to the String constructor         System out println new String new byte    b                             param args the command line arguments             public static void main String   args            new Main   convertByteToString              Output  65 65 A

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public static String readFile String fn    throws IOException        File f   new File fn        byte   buffer   new byte  int f length         FileInputStream is   new FileInputStream fn       is read buffer       is close         return  new String buffer   UTF-8       use desired encoding

User · Answer

I suggest Arrays toString byte array    It depends on your purpose  For example  I wanted to save a byte array exactly like the format you can see at time of debug that is something like this    1  2  3  If you want to save exactly same value without converting the bytes to character format  Arrays toString  byte array  does this   But if you want to save characters instead of bytes  you should use String s   new String byte array   In this case  s is equal to equivalent of  1  2  3  in format of character

User · Answer

The byte array contains characters in a special encoding  that you should know   The way to convert it to a String is   String decoded   new String bytes   UTF-8        example for one encoding type   By The Way - the raw bytes appear may appear as negative decimals just because the java datatype byte is signed  it covers the range from -128 to 127     -109   0x93  Control Code  Set Transmit State    The value  -109  is a non-printable control character in UNICODE  So UTF-8 is not the correct encoding for that character stream   0x93 in  Windows-1252  is the  smart quote  that you re looking for  so the Java name of that encoding is  Cp1252   The next line provides a test code   System out println new String new byte   -109    Cp1252

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The previous answer from Andreas D is good  I m just going to add that wherever you are displaying the output there will be a font and a character encoding and it may not support some characters   To work out whether it is Java or your display that is a problem  do this       for int i 0 i lt str length   i              char ch   str charAt i           System out println i       ch     Integer toHexString ch    ch    ufffd       Unknown character                  Java will have mapped any characters it cannot understand to 0xfffd the official character for unknown characters  If you see a     in the output  but it is not mapped to 0xfffd  it is your display font or encoding that is the problem  not Java

User · Answer

You can try this   String s   new String bytearray

[java] Converting byte array to String (Java)

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