Why should a class be designed so that its objects cannot be modified after creation?

Designing immutable objects has several advantages:

• Thread safety: Immutable objects can be safely used in multithreaded environments without synchronization.
• Simplicity of understanding: The state of the object does not change after creation, which simplifies logic and debugging.
• Predictability: No side effects when working with the object.
• Use as keys: Immutable objects can be used in collections, such as HashMap, without the risk of changing the hash code.

In Java, this is achieved, for example, by declaring all fields as final and not providing setters:

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; }
}

This class guarantees that after creation, the object will not change, which increases the reliability and safety of the code.