Converting char to byte

Question

I would like to convert a character array to a byte array in Java   What methods exists for making this conversion

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private static byte   charArrayToByteArray char   c array            byte   b array   new byte c array length           for int i  0  i  lt  c array length  i                  b array i     byte  0xFF  amp   int c array i                      return b array

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Convert without creating String object   import java nio CharBuffer  import java nio ByteBuffer  import java util Arrays   byte   toBytes char   chars      CharBuffer charBuffer   CharBuffer wrap chars     ByteBuffer byteBuffer   Charset forName  UTF-8   encode charBuffer     byte   bytes   Arrays copyOfRange byteBuffer array                byteBuffer position    byteBuffer limit       Arrays fill byteBuffer array     byte  0      clear sensitive data   return bytes      Usage   char   chars     0    1    2    3    4    5    6    7    8    9    byte   bytes   toBytes chars      do something with chars bytes    Arrays fill chars    u0000       clear sensitive data Arrays fill bytes   byte  0      clear sensitive data   Solution is inspired from Swing recommendation to store passwords in char     See Why is char   preferred over String for passwords    Remember not to write sensitive data to logs and ensure that JVM won t hold any references to it     The code above is correct but not effective  If you don t need performance but want security you can use it  If security also not a goal then do simply String getBytes  Code above is not effective if you look down of implementation of encode in JDK  Besides you need to copy arrays and create buffers  Another way to convert is inline all code behind encode  example for UTF-8    val xs  Array Char     A             toArray val len   xs length val ys  Array Byte    new Array 3   len     worst case var i   0  var j   0    i for chars  j for bytes while  i  lt  len       fill ys with bytes   val c   xs i    if  c  lt  0x80        ys j    c toByte     i   i   1     j   j   1     else if  c  lt  0x800        ys j     0xc0    c  gt  gt  6   toByte     ys j   1     0x80    c  amp  0x3f   toByte     i   i   1     j   j   2     else if  Character isHighSurrogate c         if  len - i  lt  2  throw new Exception  overflow       val d   xs i   1      val uc  Int          if  Character isLowSurrogate d             Character toCodePoint c  d          else           throw new Exception  malformed               ys j     0xf0     uc  gt  gt  18    toByte     ys j   1     0x80     uc  gt  gt  12   amp  0x3f   toByte     ys j   2     0x80     uc  gt  gt   6   amp  0x3f   toByte     ys j   3     0x80    uc  amp  0x3f   toByte     i   i   2    2 chars     j   j   4     else if  Character isLowSurrogate c         throw new Exception  malformed       else       ys j     0xe0    c  gt  gt  12   toByte     ys j   1     0x80     c  gt  gt  6   amp  0x3f   toByte     ys j   2     0x80    c  amp  0x3f   toByte     i   i   1     j   j   3          check println new String ys  0  j   UTF-8      Excuse me for using Scala language  If you have problems with converting this code to Java I can rewrite it  What about performance always check on real data  with JMH for example   This code looks very similar to what you can see in JDK 2  and Protobuf 3

User · Answer

You could make a method   public byte   toBytes char   data    byte   toRet   new byte data length   for int i   0  i  lt  toRet length  i      toRet i     byte  data i     return toRet      Hope this helps

User · Answer

char   ch     new String ch  getBytes      or  new String ch  getBytes  UTF-8      to get non-default charset   Update  Since Java 7  new String ch  getBytes StandardCharsets UTF 8

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Edit  Andrey s answer has been updated so the following no longer applies  Andrey s answer  the highest voted at the time of writing  is slightly incorrect  I would have added this as comment but I am not reputable enough  In Andrey s answer  char   chars     c    h    a    r    s   byte   bytes   Charset forName  quot UTF-8 quot   encode CharBuffer wrap chars   array     the call to array   may not return the desired value  for example  char   c    quot aaaaaaaaaa quot  toCharArray    System out println Arrays toString Charset forName  quot UTF-8 quot   encode CharBuffer wrap c   array       output   97  97  97  97  97  97  97  97  97  97  0   As can be seen a zero byte has been added  To avoid this use the following  char   c    quot aaaaaaaaaa quot  toCharArray    ByteBuffer bb   Charset forName  quot UTF-8 quot   encode CharBuffer wrap c    byte   b   new byte bb remaining     bb get b   System out println Arrays toString b     output   97  97  97  97  97  97  97  97  97  97   As the answer also alluded to using passwords it might be worth blanking out the array that backs the ByteBuffer  accessed via the array   function   ByteBuffer bb   Charset forName  quot UTF-8 quot   encode CharBuffer wrap c    byte   b   new byte bb remaining     bb get b   blankOutByteArray bb array     System out println Arrays toString b

[java] Converting char[] to byte[]

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