[java] Unsigned\Signed Trouble

Use DataInputStream.readUnsignedByte() or DataInputStream.readUnsignedShort() to get a unsigned value.

What about reading values larger than short, read two or four shorts for int and long respectively and bit shift? Obviously doable but seems a bit crude. What about byte arrays? I am reading in a byte array and still getting values interpreted as negative values. Now, obviously for a byte array I could instead loop through and read all of the data via DataInputStream.readUnsignedByte() but is there a way to continue to use DataInputStream.read() and get the whole byte array at once? Thanks.

Whether you read the data as signed or unsigned, it's still going to be the same arrangement of bits. It's only when you -use- the number that the sign bit comes into play. Here are some of the operations that are affected by the sign bit (I wish I had a complete list, anyone know of one?):

Up-casting to a larger type (for example, byte to int)
Outputting the number (println)
>, >=, <, <=
Division maybe?
Possibly more?

So if you do any of those things, you'll need special logic to make sure the number is interpreted as unsigned. But for most operations, it doesn't matter. So go ahead and read in that big array of bytes- you can remain blissfully unaware that Java thinks all those bytes should be signed.

Edit: Hmm I realized I'm being a little too vague. If you have a byte that you want to up-cast to an int, you can do something like this:

  int inty = (int) unsigned_bytey;  if (inty < 0) inty += 256;

To convert a (signed) byte to a unsigned byte in a integer, you do this

byte signedByte = -1;int unsignedByte = signedByte & 0xff;

Quote:

Original post by Isolier I know that sounds wierd but that is what is happening and because Java has no specific signed or unsigned data types

For clarity, that's not true. Java types are all signed, except for the char data type which is unsigned.