Java APIs

Well, I also used the Java Programming forum for this question,
but since nobody answered, I am using another forum. What's
really the right forum for this?

I am calling a Java native executable from a C++ program.

I would like to communicate the red, green, and blue values of an image, which are unsigned chars in my C++ program (varying between 0 and 255) to my Java program.

I first convert the unsigned chars in my C++ program to chars.

Unfortunately, chars in C++ are 1 byte and chars in Java are 2 bytes and I might have to reverse the order of bytes.

But when I recieve the char ch in Java, neither
int i = ((int)(ch)>>8) & 255
nor
int i = (int)(ch) & 255
seems to give the same value as the value of the unsigned char in C++.

What's a correct and fast way to make this communication?

Thanks for looking at this!