What is the goal when implementing a correct hashCode method in a class?

The goal of implementing a correct hashCode method in a class is to ensure the proper functioning of objects in hash data structures such as HashMap, HashSet, and Hashtable.

Main objectives:

• Ensure that equal objects (according to the equals method) return the same hash code.
• Minimize collisions so that different objects have different hash codes, which improves collection performance.

If hashCode is implemented incorrectly, objects may be stored and retrieved improperly from hash collections, leading to errors and reduced performance.

An example of a simple correct hashCode for a class with two fields:

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

It is important that hashCode and equals are consistent with each other.