Understanding TreeSet when compareto returns 0

Question

I have created a Student class like this:

public class Student implements Comparable {

    private String firstName;
    private String lastN         


        

Answer 1

Well, your treeset key values are "A1","B1","A1","A2". Even though you are not overriding equals and hashcode still the default hashcode for "A1" will be same and hence the treeset will consider this key as duplicate key so you will not be able to enter "A1","B2"