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

Hashes are simple pairing of key and values. Here's how the state of your code would look before and after the renaming in pseudo-code:

Before:

personSet => {
    SOME_NUM1 => Person(name=>"raghu", 12),
    SOME_NUM2 => Person(name=>"rimmu", 21)
}

p1.setName("raghus"); #p1.hashcode() = SOME_NEW_NUM
p1.setAge(13);#p1.hashcode() = SOME_OTHER_NEW_NUM

After:

personSet => {
    SOME_NUM1 => Person(name=>"raghu", 13),
    SOME_NUM2 => Person(name=>"rimmu", 21)
}

Since you have direct access to the p1 the object within the HashSet is updated correctly, but HashSet does not pay attention to contained objects hashcodes being updated. When a call to personSet.contains(p1) is called, the HashSet looks for an entry with the new value of p1.hashcode().

The p1 object is associated with its previous hashcode at the time when it was added to the HashSet.