Каким образом реализованы методы equals и hashCode, и какие существуют правила их взаимодействия?

In Java, the equals and hashCode methods are related and must be implemented according to certain rules:

• If two objects are equal according to equals(), they must have the same hashCode().
• If equals() returns false, then hashCode() can be the same, but minimizing collisions is desirable.

Implementation rules:

1. Override equals() to compare logical equality of objects, not just references.
2. Override hashCode() so that it aligns with the logic of equals().

Example implementation:

@Override
public boolean equals(Object o) {
    if (this == o) return true;
    if (o == null || getClass() != o.getClass()) return false;
    MyClass myClass = (MyClass) o;
    return Objects.equals(field1, myClass.field1) &&
           Objects.equals(field2, myClass.field2);
}

@Override
public int hashCode() {
    return Objects.hash(field1, field2);
}

Violating these rules can lead to incorrect behavior of collections, such as HashMap or HashSet.