Minecraft mineshaft algorithm

public static boolean hasMineshaftStartingPoint(long mapSeed, int chunkX, int chunkZ){

    Random rand = new Random();

    // *** MapGenBase->generate() / MapGenStructure->getNeareastInstance()
    rand.setSeed(mapSeed);
    long seedMod1 = rand.nextLong();
    long seedMod2 = rand.nextLong();

    long seedMod3 = (long)chunkX * seedMod1;
    long seedMod4 = (long)chunkZ * seedMod2;

    rand.setSeed(seedMod3 ^ seedMod4 ^ mapSeed);

    rand.nextInt();

    // *** MapGenMineshaft->canSpawnStructureAtCoords
    if(rand.nextDouble() < 0.01D && rand.nextInt(80) < Math.max(Math.abs(chunkX), Math.abs(chunkZ))){
        return true;
    }

    return false;
}