How to implement equals method correctly?

Consider that you are overriding equals method for Employee Class having empId, firstName and lastName.

1. Check for reference equality, if equal then return true.
2. Check for null check on the object argument being passed, if null return false.
3. Compare getClass methods, if different return false.
4. Always compare numeric and identify fields first.
5. Check for field's references first and then check for null and equality.
6. Override hashcode method whenever you override equals method.

The above steps are illustrated in the below example.

@Override
public boolean equals(Object o) {
    
    if (this == o)  // check 1
        return true;
    // null check
    if (o == null)
        return false;
    // type check and cast
    if (getClass() != o.getClass())
        return false;
    Employee emp = (Employee) o;
    //numeric and identity fields first
    if (!Objects.equals(this.emplId, emp.emplId)) return false;

    // field comparison
    return Objects.equals(firstName, emp.firstName)
            && Objects.equals(lastName, emp.lastName);
}

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