1. give an example of a hashCode algorithm ?

public int hashCode() {
  int f= 1;
  f *= 3;
  f ^= id.hashCode();
  f *= 3;
  return f;
}

2. what is the difference between concurrency and parallelism ?

https://developer.ibm.com/tutorials/reactive-in-practice-4/

3. what is async io in python?

asyncio - Asynchronous I/O - Python 3.9.5 documentation