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Java Forum / General / February 2006How to byte[ ] --> char[ ] and char[ ] --> byte[ ]?
Hello, I get a char[] from a JPasswordField and I would like to use MessageDigest.digest(byte[]) to get a md5 digest of the password. What's the best way to transform a char[] into a byte[] in Java (and to transform a byte[] into a char[])? I don't want to use a String to do that. Thanks in advance for your answers. Richard This is a way, don't know whether it's the best (guess you mean most performant) way... char[] chars = "azertyuiop".toCharArray(); byte[] bytes = new byte[10]; int i = 0; for(char c : chars) bytes[i++] = (byte)c; i = 0; for(byte b : bytes) chars[i++] = (char)b; System.out.println(chars); A thing to keep in mind is are you sure what encoding your characters are going to be? char is 16 bit. byte is 8 bit. (in java) Cheers Opalinski opalpa@gmail.com http://www.geocities.com/opalpaweb/ OK, I know that, thanks. My problem is to get a md5 digest of a password registered in a char[]. This problem seems simple but can't find a simple solution to do it. Does it exist one? Else, do you know a not so simple one? Another question: does a md5 digest can be registered in a String? Or does it contains bytes that can't be registered in a String? Cheers, Richard opalpa@gmail.com opalinski from opalpaweb a écrit : > A thing to keep in mind is are you sure what encoding your characters > are going to be? char is 16 bit. byte is 8 bit. (in java) [quoted text clipped - 4 lines] > opalpa@gmail.com > http://www.geocities.com/opalpaweb/ >Another question: does a md5 digest can be registered in a String? Or >does it contains bytes that can't be registered in a String? md5 and sha1 give you a byte[] of what appear at first to be random bytes. If you to transport that in printable format, you would need some form of armouring. See http://mindprod.com/jgloss/armouring.html http://mindprod.com/jgloss/md5.html http://mindprod.com/jgloss/sha1.html  SignatureCanadian Mind Products, Roedy Green. http://mindprod.com Java custom programming, consulting and coaching. > I don't want to use a String to do that. Any special reason why you don't want to use String to convert char[] to bytes[]. Something like this. MessageDigest.digest((new String(char[])).getBytes()); > Any special reason why you don't want to use String to convert char[] > to bytes[]. > Something like this. > MessageDigest.digest((new String(char[])).getBytes()); probably same reason why JPasswordField has deprecated method String getText() - it is unsecure BTW the simplest method to convert chars to bytes and vise versa is to use CharToByteConverter and ByteToCharConverter. SignatureAndrey Kuznetsov http://uio.imagero.com Unified I/O for Java http://reader.imagero.com Java image reader http://jgui.imagero.com Java GUI components and utilities On Tue, 31 Jan 2006 10:46:59 +0100, "Andrey Kuznetsov" <spam0@imagero.com.invalid> wrote, quoted or indirectly quoted someone who said : >BTW the simplest method to convert chars to bytes and vise versa >is to use CharToByteConverter and ByteToCharConverter. If you look at the String methods you might be horrified to see how much copying and creating of intermediate objects goes on during byte[] <=> String conversion.. These new methods can avoid much of that overhead. SignatureCanadian Mind Products, Roedy Green. http://mindprod.com Java custom programming, consulting and coaching. > On Tue, 31 Jan 2006 10:46:59 +0100, "Andrey Kuznetsov" > <spam0@imagero.com.invalid> wrote, quoted or indirectly quoted someone [quoted text clipped - 7 lines] > byte[] <=> String conversion.. These new methods can avoid much of > that overhead. byte[] <=> char[] conversion is hard to generalize, and yet String presents a pretty simple, general interface to the process. And String has that darn immutible property to maintain, so I would expect that the conversion routines in String to be less than totally efficient. -- Adam Maass >I get a char[] from a JPasswordField and I would like to use >MessageDigest.digest(byte[]) to get a md5 digest of the password. What's >the best way to transform a char[] into a byte[] in Java (and to >transform a byte[] into a char[])? see http://mindprod.com/jgloss/conversion.html SignatureCanadian Mind Products, Roedy Green. http://mindprod.com Java custom programming, consulting and coaching. > I get a char[] from a JPasswordField and I would like to use > MessageDigest.digest(byte[]) to get a md5 digest of the password. What's > the best way to transform a char[] into a byte[] in Java (and to transform > a byte[] into a char[])? You need to decide which /encoding/ you are going to use to do the transformation from char[] to byte[] (and back again). char is 16-bits; byte is 8-bits; there are any number of ways to map the 16-bit values onto 8-bit values. One such encoding is ASCII (though based on the .fr domain in your email, probably not a good choice). Then the code to get a byte[] from a char[] is very simple: byte[] bytes = new String(chars).getBytes("ASCII"); There is also the not-quite analogous getChars method... String str = new String(bytes, "ASCII"); char[] chars = new char[str.length()]; str.getChars(0, chars.length, chars, chars.length); > I don't want to use a String to do that. The String class has the very handy getBytes() and getChars() methods, so you probably want to take advantage of that. Or you could look at the source for those methods and replicate it... -- Adam Maass > The String class has the very handy getBytes() and getChars() methods, so > you probably want to take advantage of that. Or you could look at the > source for those methods and replicate it... till java 1.4 they used CharToByteCoverter and ByteToCharConverter. SignatureAndrey Kuznetsov http://uio.imagero.com Unified I/O for Java http://reader.imagero.com Java image reader http://jgui.imagero.com Java GUI components and utilities Free MagazinesGet these publications absolutely FREE for up to 12 months. There are no hidden fees and no obligation. Simply choose a title, complete the application form and submit it. Read more ...
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