converting an array of signed bytes to unsigned bytes [duplicate]

Question

I have a array of bytes.

bytes[] = [43, 0, 0, -13, 114, -75, -2, 2, 20, 0, 0]

I want to convert it to unsigned bytes in Java. this is what I did: created a new array and copy the values with & 0xFF:

    this.bytes = new byte[bytes.length];
    for (int i=0;i<bytes.length;i++)
        this.bytes[i] = (byte) (bytes[i] & 0xFF);

but the values stay negative in the new array as well. what am I doing wrong?

What do you expect an operation like byteValue & 0xFF to do? — f1sh
– f1sh, Commented Oct 26, 2017 at 8:56
@f1sh It does the right thing in terms of converting a signed byte into an unsiged int. If you just cast a byte with a negative value e.g. into an int you end up with an int with that negative number. So that part of the code wasn't the problem, just the one where it's put back (i.e. casted again) into a byte ending up with the same negative value you started with. — Lothar
– Lothar, Commented Oct 26, 2017 at 9:09

Eran · Accepted Answer · 2017-10-26 08:54:36Z

14

bytes in Java are always signed.

If you want to obtained the unsigned value of these bytes, you can store them in an int array:

byte[] signed = {43, 0, 0, -13, 114, -75, -2, 2, 20, 0, 0};
int[] unsigned = new int[signed.length];
for (int i = 0; i < signed.length; i++) {
    unsigned[i] = signed[i] & 0xFF;
}

You'll get the following values:

[43, 0, 0, 243, 114, 181, 254, 2, 20, 0, 0]

answered Oct 26, 2017 at 8:54

Eran

395k57 gold badges726 silver badges793 bronze badges

Sign up to request clarification or add additional context in comments.

1 Comment

Ohad Over a year ago

I understand. thanks! in python there is, that's why got mistaken..

Lothar · Accepted Answer · 2017-10-26 08:54:00Z

1

Java has no thing called an unsigned byte. You have to use other types like short or int to be able to hold values > 127.

answered Oct 26, 2017 at 8:54

Lothar

5,4591 gold badge14 silver badges27 bronze badges

Collectives™ on Stack Overflow

converting an array of signed bytes to unsigned bytes [duplicate]

2 Answers 2

1 Comment

Comments

Linked

Hot Network Questions

Collectives™ on Stack Overflow

2 Answers 2

1 Comment

Comments

Linked

Related