Convert short to byte[] in Java

Question

How can I convert a short (2 bytes) to a byte array in Java, e.g.

short x = 233;
byte[] ret = new byte[2];

...

it should be s

Answer 1

It depends how you want to represent it:

• big endian or little endian? That will determine which order you put the bytes in.

• Do you want to use 2's complement or some other way of representing a negative number? You should use a scheme that has the same range as the short in java to have a 1-to-1 mapping.

For big endian, the transformation should be along the lines of: ret[0] = x/256; ret[1] = x%256;

Answer 2

Several methods have been mentioned here. But which one is the best? Here follows some proof that the following 3 approaches result in the same output for all values of a short

  // loops through all the values of a Short
  short i = Short.MIN_VALUE;
  do
  {
    // method 1: A SIMPLE SHIFT
    byte a1 = (byte) (i >> 8);
    byte a2 = (byte) i;

    // method 2: AN UNSIGNED SHIFT
    byte b1 = (byte) (i >>> 8);
    byte b2 = (byte) i;

    // method 3: SHIFT AND MASK
    byte c1 = (byte) (i >> 8 & 0xFF);
    byte c2 = (byte) (i & 0xFF);

    if (a1 != b1 || a1 != c1 ||
        a2 != b2 || a2 != c2)
    {
      // this point is never reached !!
    }
  } while (i++ != Short.MAX_VALUE);

Conclusion: less is more ?

byte b1 = (byte) (s >> 8);
byte b2 = (byte) s;

(As other answers have mentioned, watch out for LE/BE).

Answer 3

An alternative that is more efficient:

    // Little Endian
    ret[0] = (byte) x;
    ret[1] = (byte) (x >> 8);

    // Big Endian
    ret[0] = (byte) (x >> 8);
    ret[1] = (byte) x;