128 bit representation and primitives in java

Question

I need to represent 128 bit int key in java, like

0x9c1f03a0d9cf510f2765bd0f226ff5dc

I know how represent 128 bit variable in theory.. cut into 2 64 bit int or four 32 bit int.

But i need this representation for compare keys (k1 < k2 and k1 == k2) and i dont know how doing that with a key splitted into severals int, and i dont know how split my hexa key into 2 or 4 int either..

I am totally ignorant with bit manipulation and transformation, some explanations would be very useful

Answer 1

Fantastic news! Java provides an arbitrary precision integral type. The BigInteger(String, int) constructor can be used to take your hex and make a 128-bit value. Further BigInteger is Comparable. You could use it like,

BigInteger bi = new BigInteger("9c1f03a0d9cf510f2765bd0f226ff5dc", 16);
BigInteger bi2 = bi.add(BigInteger.ONE);
if (bi2.compareTo(bi) > 0) {
    System.out.println("Like this");
}

Outputs

Like this