Where else is it convenient to use immutable objects besides as keys in HashMap?

Immutable objects are convenient not only as keys for HashMap but also in the following cases:

• Parallel programming: Immutable objects are safe to use in a multithreaded environment without additional synchronization.
• Caching: Immutable objects can be safely cached without fear of their modification.
• Data transfer between layers or services: Immutability guarantees that data will not be changed after creation.
• Use in collections: for example, as elements in a Set or as values where it is important to avoid unintentional changes.
• Functional programming: Immutable objects facilitate the implementation of pure functions and code predictability.

Example of creating an immutable class in Java:

public final class Person {
    private final String name;
    private final int age;

    public Person(String name, int age) {
        this.name = name;
        this.age = age;
    }

    public String getName() {
        return name;
    }

    public int getAge() {
        return age;
    }
}