HashSet contains problem with custom objects

Question

My Custom class that will be contained by HashSet

public class Person {
    String name;
    int age;

    public Person(String name, int age) {
        this         


        

Answer 1

HashSet implements Set. The ApiDoc specifies:

Note: Great care must be exercised if mutable objects are used as set elements. The behavior of a set is not specified if the value of an object is changed in a manner that affects equals comparisons while the object is an element in the set.

In your example this is the case, because changing name or age on p1 affects equal-comparison. So according the ApiDoc, the behavior of Set in your case is unspecified.