What is an immutable class? What are its disadvantages?

Immutable class is a class whose instances cannot be changed after creation. All fields are usually declared as final and initialized in the constructor.

Advantages:

• Thread safety without additional synchronization.
• Simplicity of understanding and debugging.
• Used as keys in collections.

Disadvantages:

• When modifying an object, a new instance must be created, which can lead to increased memory usage and reduced performance.
• Not always convenient for objects with many fields or complex hierarchy.

Example of 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; }
}