How to convert A string that represents an integer to unsigned byte array in Java?

Question

Basically, what I want is to convert a string like "123456" to unsigned byte array: [1, 226, 64]. However, I look everywhere and what I found is to get the 2's complements (signed) byte array [1, -30, 64]:

byte[] array = new BigInteger("123456").toByteArray();
System.out.println(Arrays.toString(array));

OUTPUT:

[1, -30, 64]

So, how can it be done in Java? I want the output to be:

[1, 226, 64]

EDIT: I know that byte can hold only up to 127, so instead of byte array I need it to be int array.

There is no unsigned byte type in Java, therefore you'll have to convert it into signed short/int array. — Crozin
– Crozin, Commented Mar 5, 2012 at 21:24

Eng.Fouad · Accepted Answer · 2012-03-06 12:33:27Z

4

Java has no unsigned types, so you'll have to store the values in an int array.

byte[] array = new BigInteger("123456").toByteArray(); 
int[] unsigned_array = new int[array.length]; 
for (int i = 0; i < array.length; i++) { 
    unsigned_array[i] = array[i] >= 0 ? array[i] : array[i] + 256;
}

Fairly straightforward.

edited Mar 6, 2012 at 12:33

Eng.Fouad

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answered Mar 5, 2012 at 21:28

Mihai

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DNA · Accepted Answer · 2012-03-06 11:00:45Z

2

Java does not have unsigned bytes, so to convert them to ints as if they were unsigned, you need to AND them bitwise (&) with int 0xFF:

byte[] array = new BigInteger("123456").toByteArray();
for (int i = 0; i < array.length; i++) { 
    System.out.println(0xFF & array[i]);
}

Output:

1
226
64

You don't necessarily need to store them as an int array - it depends what you want to do with them...

edited Mar 6, 2012 at 11:00

answered Mar 5, 2012 at 21:26

DNA

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