Java ByteBuffer to String

Question

Is this a correct approach to convert ByteBuffer to String in this way   String k    abcd   ByteBuffer b   ByteBuffer wrap k getBytes     String v   new String b array      if k equals v       System out println  it worked    else     System out println  did not work      The reason I ask is that is this looks too simple  whereas other approaches like Java  Converting String to and from ByteBuffer and associated problems looks more complex

User · Answer

The answers referring to simply calling array() are not quite correct: when the buffer has been partially consumed, or is referring to a part of an array (you can ByteBuffer.wrap an array at a given offset, not necessarily from the beginning), we have to account for that in our calculations. This is the general solution that works for buffers in all cases (does not cover encoding):

if (myByteBuffer.hasArray()) {
    return new String(myByteBuffer.array(),
        myByteBuffer.arrayOffset() + myByteBuffer.position(),
        myByteBuffer.remaining());
} else {
    final byte[] b = new byte[myByteBuffer.remaining()];
    myByteBuffer.duplicate().get(b);
    return new String(b);
}

For the concerns related to encoding, see Andy Thomas' answer.

User · Answer

Just wanted to point out  it s not safe to assume ByteBuffer array   will always work   byte   bytes  if buffer hasArray          bytes   buffer array      else       bytes   new byte buffer remaining         buffer get bytes     String v   new String bytes  charset     Usually buffer hasArray   will always be true or false depending on your use case  In practice  unless you really want it to work under any circumstances  it s safe to optimize away the branch you don t need  But the rest of the answers may not work with a ByteBuffer that s been created through ByteBuffer allocateDirect

User · Answer

There is simpler approach to decode a ByteBuffer into a String without any problems  mentioned by Andy Thomas    String s   StandardCharsets UTF 8 decode byteBuffer  toString

User · Answer

the root of this question is how to decode bytes to string   this can be done with the JAVA NIO CharSet   public final CharBuffer decode ByteBuffer bb    FileChannel channel   FileChannel open    Paths get  files text-latin1 txt   StandardOpenOption READ   ByteBuffer buffer   ByteBuffer allocate 1024   channel read buffer    CharSet latin1   StandardCharsets ISO 8859 1  CharBuffer latin1Buffer   latin1 decode buffer    String result   new String latin1Buffer array        First we create a channel and read it in a buffer Then decode method decodes a Latin1 buffer to a char buffer We can then put the result  for instance  in a String

User · Answer

Notice  aside from the encoding issue  that some of the more complicated code linked goes to the trouble of getting the  active  portion of the ByteBuffer in question  for example by using position and limit   rather than simply encoding all of the bytes in the entire backing array  as many of the examples in these answers do

User · Answer

Convert a String to ByteBuffer  then from ByteBuffer back to String using Java    import java nio charset Charset  import java nio     String babel    obufscate thd   alphebat and yolo     System out println babel     Convert string to ByteBuffer  ByteBuffer babb   Charset forName  UTF-8   encode babel   try        Convert ByteBuffer to String     System out println new String babb array     UTF-8       catch Exception e       e printStackTrace        Which prints the printed bare string first  and then the ByteBuffer casted to array     obufscate thd   alphebat and yolo   obufscate thd   alphebat and yolo     Also this was helpful for me  reducing the string to primitive bytes can help inspect what s going on   String text              convert utf8 text to a byte array byte   array   text getBytes  UTF-8      convert the byte array back to a string as UTF-8 String s   new String array  Charset forName  UTF-8     System out println s     forcing strings encoded as UTF-8 as an incorrect encoding like   say ISO-8859-1 causes strange and undefined behavior String sISO   new String array  Charset forName  ISO-8859-1     System out println sISO     Prints your string interpreted as UTF-8  and then again as ISO-8859-1

User · Answer

Here is a simple function for converting a byte buffer to string  public String byteBufferToString ByteBuffer bufferData        byte   buffer   new byte bufferData readableByteCount            read bufferData and insert into buffer      data read buffer          CharsetUtil supports UTF 16  ASCII  and many more     String text   new String buffer  CharsetUtil UTF 8       System out println  quot Text   quot  text       return text

User · Answer

Try this   new String bytebuffer array     ASCII      NB  you can t correctly convert a byte array to a String without knowing its encoding   I hope this helps

User · Answer

EDIT  2018   The edited sibling answer by  xinyongCheng is a simpler approach  and should be the accepted answer   Your approach would be reasonable if you knew the bytes are in the platform s default charset  In your example  this is true because k getBytes   returns the bytes in the platform s default charset   More frequently  you ll want to specify the encoding  However  there s a simpler way to do that than the question you linked  The String API provides methods that converts between a String and a byte   array in a particular encoding  These methods suggest using CharsetEncoder CharsetDecoder  when more control over the decoding  encoding  process is required    To get the bytes from a String in a particular encoding  you can use a sibling getBytes   method   byte   bytes   k getBytes  StandardCharsets UTF 8      To put bytes with a particular encoding into a String  you can use a different String constructor   String v   new String  bytes  StandardCharsets UTF 8      Note that ByteBuffer array   is an optional operation  If you ve constructed your ByteBuffer with an array  you can use that array directly  Otherwise  if you want to be safe  use ByteBuffer get byte   dst  int offset  int length  to get bytes from the buffer into a byte array

User · Answer

private String convertFrom String lines  String from  String to        ByteBuffer bb   ByteBuffer wrap lines getBytes         CharBuffer cb   Charset forName to  decode bb       return new String Charset forName from  encode cb  array        public Doit        String concatenatedLines   convertFrom concatenatedLines   CP1252    UTF-8

[java] Java ByteBuffer to String

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