CODEWITHSUNDEEP
javastringarraysascii
Steve
Steve

Reputation: 350

Java String to byte conversion issue

I have some test code which is not working as I expect, after reviewing various sites and specifications I still cannot figure out what is happening.

Here is my test code:

byte[] b = new byte[8];
b[0] = (byte)0x72;
b[1] = (byte)0x3A;
b[2] = (byte)0x60;
b[3] = (byte)0x01;
b[4] = (byte)0x0E;
b[5] = (byte)0x10;
b[6] = (byte)0x8A;
b[7] = (byte)0x11;
String bitmapStr = new String(b);
try {
    b = bitmapStr.getBytes("US-ASCII");
} catch (Exception ex) {
    ex.printStackTrace();
}
System.out.println("DEBUG: bitmapStr = \"" +bitmapStr + "\"");
for (int i=0; i<=7; i++) {
    int byte1 = b[i];
    System.out.println("byte"+i + ": " + Integer.toHexString(byte1));
}

When I run the program I get the following in the console output:

DEBUG: bitmapStr = "r:`�"
byte0: 72
byte1: 3a
byte2: 60
byte3: 1
byte4: e
byte5: 10
byte6: 3f
byte7: 11

See how byte6 i.e. b[6] from my byte array outputs 0x3F, but it should be 0x8A.

Any ideas why?

By the way, if I use UTF-8 encoding I get an even more funky output (although ASCII is correct).

UTF-8 String encoding output:

byte0: 72
byte1: 3a
byte2: 60
byte3: 1
byte4: e
byte5: 10
byte6: ffffffef
byte7: ffffffbf

Upvotes: 3

Views: 1384

Answers (4)

Chris Gerken
Chris Gerken

Reputation: 16392

Try another form of the String constructor:

String bitmapStr = new String(b,"ISO-8859-1");

Upvotes: 5

Alex
Alex

Reputation: 1659

You are forcing hexadecimal become byte ( 8 bits ). This is called casting and you cannot do that. You notice that all values have a good output except when 0xYZ where Y >=8 ! do not use casting unless you're sure you're not gonna lose information.

Upvotes: 1

Steve
Steve

Reputation: 350

Following the suggestions from Rahul and irreputabe I figured it out:

When I changed to UTF-16LE / ISO-8859-1 encoding, byte6 was output as: "ffffff8a", then I realised I was performing a type conversion from byte to int here:

int byte1 = b[i];

So I just added:

int byte1 = b[i] & 0xFF;

for the correct result.

Upvotes: 0

Rahul Tripathi
Rahul Tripathi

Reputation: 172398

Try something like this to change a string to byte:-

  String source = "2675326";
 byte[] byteArray = source.getBytes("UTF-16LE");

or change your code to:-

 String bitmapStr = new String(b,"US-ASCII");

Upvotes: 2

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