Java hashcode from multiple fields

In view of such a class:

class MyObject {
  private String id1;
  private String id2;

  @Override
  public boolean equals(Object o) {
    if (o == this) return true;
    if (!(o instanceof MyObject)) {
        return false;
    }
    MyObject other = (MyObject) o;
    return id1.equals(other.id1) || id2.equals(other.id2);
  }
}

Note that equality does not depend on two field matches, both fields are valid What is the appropriate hashcode implementation for this class?

Solution

This is not an effective implementation of equals

Specifically, it violates the transitivity requirement

Therefore, in addition to having all instances have the same hash code, you cannot "correctly" implement hashcode