What methods can be used to implement a key class for HashMap to reduce the likelihood of collisions?

To reduce the likelihood of collisions in HashMap, the key class should correctly implement the equals() and hashCode() methods.

Main recommendations:

• hashCode() should return a well-distributed value, considering all fields that influence the uniqueness of the object.
• Use a combination of fields with multipliers and addition to obtain diverse hash codes.
• equals() should accurately compare all significant fields.

Example in Java:

@Override
public int hashCode() {
    int result = 17;
    result = 31 * result + (field1 != null ? field1.hashCode() : 0);
    result = 31 * result + field2;
    return result;
}

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

This approach reduces collisions and improves HashMap performance.