private long hash(final int x,final int k){
  return (((a[k] * x) ^ b[k]) & 0x7FFFFFFFFFFFFFFFL) % m;
}

private long hash ( final int x , final int k ) { return ( ( ( a [ k ] * x ) ^ b [ k ] ) & 0x7FFFFFFFFFFFFFFFL ) % m ; }
hashes the given integer with the given hash function .
