Java char contains value > 255 ?

Question

Hi,

I get a char array from a socket :

char[] cbuf = new char[3];
inputStream.read(cbuf, 0, 3); // read 3 chars in buffer "cbuf", offset = 0

Then when I print that :

System.out.println("r:"+(int)cbuf[0]+" g:"+(int)cbuf[1]+" b:"+(int)cbuf[2]);

I get at some point :

...
r:82 g:232 b:250
r:82 g:232 b:250
r:66 g:233 b:8224

The 8224 value is way more than 255, how can a char contain this value ???

Thank you

Answer 1

The char type in Java is 16-bit.

If you are looking for an 8 bit datatype consider using byte.

Answer 2

Java uses UTF (not ASCII) to store chars, UTF is 16-bits long so it can contain values up to 65.535.

Answer 3

The char primitive in Java in 16 bits wide, to accommodate characters outside the standard ASCII range, using Unicode.

It looks like you're trying to store RGB values in a char[3]. May I suggest a byte[3], or java.awt.Color?

Color c = new Color(255, 255, 240);

Answer 4

There is no read(char[], int, int) method on InputStream. You must be calling that on a Reader sub-class (such as InputStreamReader). InputStreamReader automatically converts bytes to characters using the platform default character encoding which in your case looks like it's windows-1252.

The character you received, 8224 is Unicode character U+2020 Dagger '†'. This was probably translated from byte 0x86 (134) using the windows-1252 character encoding.

If you're reading a file containing stuff that isn't text, you need to make sure that you don't read it with a subclass of Reader but use a subclass of InputStream instead. Alternatively, you can use an InputStreamReader and specify a character encoding like ISO-8859-1 that will map every byte to a char with the same numeric value.

Answer 5

As people have already pointed out, you want to read bytes, not chars (chars are 16 bits in Java), and make sure you are actually using an InputStream and not a Reader.

I also want to point out something that is not directly related to your question: When calling InputStream.read(byte[]) or InputStream.read(byte[], int, int) to read several bytes, do not assume that all requested bytes have been read upon return. The call to read may return as soon as some bytes are available. You should always check the return value to find out how many bytes have actually been read.

The same applies to the read methods in Reader.