What methods can be used to implement immutability of classes in programming?

To implement immutable classes in Java, the following methods are usually used:

1. Declare the class as final to prevent inheritance and behavior modification.
2. Make all fields private and final so they cannot be changed after initialization.
3. Do not provide setters (methods to modify fields).
4. Initialize all fields through the constructor.
5. If fields contain references to mutable objects, create copies of them when passing to the constructor and when returning from getters (protection against external modifications).

Example:

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

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

    public String getName() {
        return name;
    }

    public int getAge() {
        return age;
    }
}

Such a class, after object creation, does not allow changing its state.