what's a fast way to convert an Integer
into a Byte Array
?
e.g. 0xAABBCCDD => {AA, BB, CC, DD}
Have a look at the ByteBuffer class.
ByteBuffer b = ByteBuffer.allocate(4);
//b.order(ByteOrder.BIG_ENDIAN); // optional, the initial order of a byte buffer is always BIG_ENDIAN.
b.putInt(0xAABBCCDD);
byte[] result = b.array();
Setting the byte order ensures that result[0] == 0xAA
, result[1] == 0xBB
, result[2] == 0xCC
and result[3] == 0xDD
.
Or alternatively, you could do it manually:
byte[] toBytes(int i)
{
byte[] result = new byte[4];
result[0] = (byte) (i >> 24);
result[1] = (byte) (i >> 16);
result[2] = (byte) (i >> 8);
result[3] = (byte) (i /*>> 0*/);
return result;
}
The ByteBuffer
class was designed for such dirty hands tasks though. In fact the private java.nio.Bits
defines these helper methods that are used by ByteBuffer.putInt()
:
private static byte int3(int x) { return (byte)(x >> 24); }
private static byte int2(int x) { return (byte)(x >> 16); }
private static byte int1(int x) { return (byte)(x >> 8); }
private static byte int0(int x) { return (byte)(x >> 0); }