Could you give an example of a class that is immutable after creation?

An example of an immutable class in Java is the String class. To create your own immutable class, you need to:

• Make the class final so it cannot be subclassed and its behavior cannot be changed.
• Make all fields private final.
• Initialize all fields through the constructor.
• Do not provide setters.
• If the fields are objects, ensure their immutability or return copies.

Example of a simple immutable class:

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;
    }
}

Once a Person object is created, its state cannot be changed.