Converting InputStream.read() to numbers (not integers)

Question

I've been struggling to get a part of my program working. After about a week of trial and error I don't think I'm able to do this without any help.

Here's the case: I've written an application which, using Sockets, reads data from a device over TCP . All the data sent by the device is represented as bytes, not as strings. Whenever I google on InputStream , all I get is "How to convert InputStream to String".

Currently I'm able to read the data from the InputStream into an ArrayList<Integer> . However, these are Integers, and not decimals.

Here's an example of a (UNIX) TimeStamp sent by the device, read in integers:

0 0 1 80 59 165 176 64 (edited, copied 1 byte too many)

I've tried a lot here, and have not yet succeeded in converting these to a correct UNIX timestamp. It should be translated to 1444109725 (which is 10/06/2015 @ 5:35am (UTC)) .

Anyone who could help me out? Thanks in advance!

-- Edit --

Thanks to all the answers below I've been able to create a working 'parser' for the incoming data. All I had to do was convert the bytes/integers to Long values. As my incoming data consists of multiple values with different lengths it's not possible to read it all as Long, so I had to iterate over te data, grab for example the 8 bytes/integers for the timestamp and use this method to create a readable unix timestamp:

public long bytesToLong(int[] bytes) { 
long v = 0 ; 
for (int i : bytes) { 
v = (v << 8) | i; 
} return v; 
}

Answer 1

It should be translated to 1444109725

Well, I suspect it should actually be translated to 1444109725760, which is what the bytes represent when read as a big-endian 64-bit integer. You then treat that as milliseconds since the Unix epoch (rather than seconds).

Fortunately, this is trivial to do: use DataInputStream , and call readLong . It would be slightly trickier if this were little-endian... but if your format is basically big-endian, you should do as much as you can using DataInputStream ... it'll make your life much simpler.

Answer 2

Agree with the previous answer, using DataInputStream is the best way to go. If you want to get the value by hand:

package snippet;

public class FindLong {

    public static void main(String[] args) {
        int[] bytes = new int[] { 0, 0, 1, 80, 59, 165, 176, 64 } ;

        long v = 0 ;
        for (int i : bytes) {
            v = (v << 8) | i;
        }
        System.out.println(v);
    }
}

Prints 1444109725760 .