String to byte array conversion varies from windows and ubuntu

Question

public static void main(String args[])
    {       
        byte[] bytearray = new byte[]{1, -30, 48, 50, 49, 48};

        for (int i = 0; i < bytearray.length; i++) {
            System.out.print(bytearray[i]+", ");
        }
        System.out.println();
        System.out.println("Length of byteArray before : "+bytearray.length);

        String st = new String(bytearray);
        System.out.println("String value : "+ st);  

        bytearray = st.getBytes();

        for (int i = 0; i < bytearray.length; i++) {
            System.out.print(bytearray[i]+", ");
        }
        System.out.println();
        System.out.println("Length of byteArray after : "+bytearray.length);
    }

this is my program if i am executing this on windows i am getting exactly same bytes as previous but on ubuntu, it's giving extra 2 bytes I didn't understand it ? why ?

which method should I use to get same array on ubuntu ?

I think you can fix that by using the same character set. Here is an example: new String(bytearray, "UTF-8") and str.getBytes("UTF-8"). — Titus
– Titus, Commented Oct 24, 2016 at 10:59

Peter Lawrey · Accepted Answer · 2016-10-24 12:11:15Z

2

Sorry, I thought you were using valid encoded data.

Your bytes are not valid UTF-8, so if you have different versions of Java it may handle this differently.

new byte[]{1, -30, 48, 50, 49, 48}

In short your should be using text to attempt to store binary data. This will only confuse you (and waste memory)

edited Oct 24, 2016 at 12:11

answered Oct 24, 2016 at 10:58

Peter Lawrey

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6 Comments

Shailesh Over a year ago

I am working on ubuntu and it's throwing java.io.UnsupportedEncodingException if I am using StandardCharsets.UTF_8

Peter Lawrey Over a year ago

@Shailesh There is something wrong with your JVM then, as it's a standard builtin encoding all JVMs have to have which is why it's in the StandardCharsets. docs.oracle.com/javase/8/docs/api/index.html?java/nio/charset/… note: If you use a String you have to write "UTF-8"

Shailesh Over a year ago

it's giving default charset as utf-8, i have tried using "UTF-8" still it's not working..! are you sure there is something wrong with my JVM ?

Shailesh Over a year ago

sorry but I didn't get that ideone.com link program how it shows JVM is wrong ?

Peter Lawrey Over a year ago

@Shailesh Sorry, I realised what the problem is. You can't be encoding binary data as text unless you like confusion (or you really know what you are doing) I strongly suggest you avoid trying to do this. Different versions of Java and different encoding handle invalid encoded bytes differently.

|

uoyilmaz · Accepted Answer · 2016-10-24 11:00:26Z

1

Here is what the documentation says for String constructor:

Constructs a new String by decoding the specified array of bytes using the platform's default charset.

And what it says for getBytes:

Encodes this String into a sequence of bytes using the platform's default charset, storing the result into a new byte array.

So, why do you get different behavior in different systems? Because their default charsets are different. You can get the default charset using Charset.defaultCharset().

answered Oct 24, 2016 at 11:00

uoyilmaz

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3 Comments

Shailesh Over a year ago

I have tried this it's giving default charset as UTF-8, and still the problem exist...!

uoyilmaz Over a year ago

Try using String st = new String(bytearray, "ISO-8859-1") and bytearray = st.getBytes( "ISO-8859-1")

Peter Lawrey Over a year ago

Even though you can do this, it's likely to be a bad idea unless you know the bytes are a String encoded as ISO-8859-1.

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