Best implementation for hashCode method for a collection

Question

How do we decide on the best implementation of hashCode() method for a collection (assuming that equals method has been overridden correctly) ?

Answer 1

If you're happy with the Effective Java implementation recommended by dmeister, you can use a library call instead of rolling your own:

@Override
public int hashCode() {
    return Objects.hashCode(this.firstName, this.lastName);
}

This requires either Guava (com.google.common.base.Objects.hashCode) or the standard library in Java 7 (java.util.Objects.hash) but works the same way.